Thanks for your comments and taking the time to read the rules and intending to build your own version. I understand that it's not an easy task, especially if you don't konw if it's worth the effort.
So let's tackle your questions:
Couple questions/comments: If I roll the D100 first, and get a critical success or critical failure than the modifiers don't apply? Much like rolling a 1 in BB? Or can the modifiers increase the critical failure so that it goes to the next level? I ask only because the rules could be cleaned up in that section if the modifiers don't apply on a critical.
The first part is correct. If you roll a critical, the roll automatically counts as a critical success or critical failure and the modifiers have no effect on the outcome.
The intention of this rule is to retain a bit of tension even if you make the perfect play. Like in the boardgame your 3D Block with a reroll will fail sometimes. It also gives players a last-ditch attempt should everthing else fail. Statistically it is highly unlikely to change the outcome of the match but it should help to keep the hopes of the losing player up and might be good for a laugh once in a while.
Did you look at using something other than a D100? (I'm sure you did, just curious how you ended up at that?) Seems like it makes the Play Test a bit more daunting than it needs to be. Having to add up 5 numbers than subtracting 5 numbers and adding modifiers from the cards, etc. Just seems like there could be a way to make it more streamlined.
Good point and one I was expecting, as this is one of the things that I am not entirely satisfied with myself.
I did look into other ways but I always came back to this rather complex method. Let me try to explain the ideas behind my train of thought:
The players and their abilities should be an integral part of the game, i.e. the composition of the team and the players on the pitch should have a noticable effect on the game. The idea behind this is that this game supports a large (more than 100) number of distinct player cards which allow for individual team composition and playstyles. Another reason is that taking single players out via Blocks or Blitzes should be a viable strategy and therefore is only viable if the player that is taken out has an effect on the game.
One way to incorporate these effects is by assigning different stats, that are relevant to the game, to each player. This is the one I have chosen for this ruleset, because I didn't come up with a better idea that allows for the kind of gameplay I intended.
So what else could be done to make the Play Test simpler?!
1) Why a D100?: The effect of each player on the game has to be on the one hand noticeable and on the other hand not so grave as to break the game.Therefore the range of results has to allow for these kind of modifications. The percentage system (D100) was chosen because it fits the requirement and is rather sleek (compared to the D68 used for the casualty table in BB for example). The next common system would have been the D20 system which in my opinion is too grainy for the game. For example a stat of +1 (D20) equals +5%; which in the current system is a rather large modifier, beacuse with 5 players on the field this could potentially mean +25% to the play test!
2) Why 5 Players?: I chose the number 5 for the (star) players on pitch because the number is convenient. It is high enough to allow for distinct play teams but not so high as to be unwieldy. Btw, the intention of the game is not to pretend that BB is a 5 on 5 game. Both teams are still made up of 11 players on the pitch but for gameplay reasons only 5 of them are represented by player cards. Just pretend that these are the top players (stars) of the team which make or break the team and are supported by the rest of the team which for the purpose of playability have no direct influence on the game.
3) Why splitting the stats into offense and defense?: The way the game currently works, the differentiation between offensive and defensive stats provides the game with balance and symmetry, which is reflected in the tests that all work in the same way and for the most part elegantly take both sides (offense and defense) into account. Another positive side effect is that this gives room for more distinct players and allows for defensive positionals.
4) Streamlining it somehow: If you have any idea, you are welcome.
If your intent is to include a "playmat" may I suggest just including counters for the coaching staff and RR's? Just to cut down on the amount of cards you would need to print, yeah, I know its a card game... just a thought.
The idea behind the cards is that they make the game easily expandable (if it was a true Trading Card Game, cards are easier to distribute than counters) and that they provide room to state the effect of the card. Also from an aesthetic point of view I prefer the cards.
But there is nothing wrong with counters. The way to handle these things is really up to the players. If you have a copy of BB you could use the counters included in there for example or write your additional staff on a piece of paper. Whatever is convenient for both players is ok.
The inclusion of the playmat evolved from the 'scoreboard' and is more or less just a fancy way to organise the play area.
Another general comment, there seem to be way too many abbreviations... Z, B, P, R, SR, CF, KD, CS... its a bit overwhelming at first and difficult to interpret. Not a big deal as a final version could handle some of that with art work (icons) or actually write out the stats instead of Z, just use Blitz.
The main reason for the abbrevations is the limited space on the cards. Especially if the game should be able to support special cards that don't comply with the standard rules (see cards 031 to 035 for examples), abbrevations are neccessary to fit the text in a readable size on the card.
The inclusion of art work would not really help as the icons would have to be also learned at first to understand their meaning.
In the case of the play abbrevations (Z B P R), their meaning is actually not relevant for the gameplay. It doesn't matter if you know that the P-symbol for example stands for 'Pass' when you play the card, because all relevant stats feature the same symbol.
But your point still stands and I will consider this to make the rules easier to understand.
Just some comments, don't take them as anything more than a first impression of reading through the rules and all the cards. I may print it out in black and white and give it a go just to see how it plays.
Let's hope the cards are suitable for black and white printing. I fear that the lack of color coding (red for offense/ blue for defense) will make the game a bit harder to learn.
Great job, lots of work here, would be cool if you could dump the BB from it and make it a more generic FFB game so that you could actually market it.

Looks like you have a lot of potential to build on it as well, everything from Stars to the rest of the teams, to more players to maybe even inducements.
I have to admit that dumping the BB references and marketing it came to my mind but that would have been illusionary as it is not that easy and the quality of the game is still up in the air. Its a hobby, so better leave it at that before it starts to become work!
Also if it wasn't for my passion of BB, I wouldn't have put that much work into it in the first place I presume.
Edit: I created a pdf of ALL the cards that need to be printed (33 pages), I have it on Google docs. If Physix gives the ok I can share it. Or I can give it to Physix and he can share it. Its nothing special, I just did it so I could click print once and have everything I need.
That's very nice of you and I wouldn't mind if they are shared. But I would prefer to host them myself, so that it is easier for me to pull the files when grandma wendy shows her ugly face.