You were not fired for NO REASON. You were fired because you didn't pass 2 of the required 6 tests. I would also bet that the additional tests they wanted you to take was in fact a re-take of the 2 tests you failed. Think of this another way, if you got 4 of 6 numbers in the lottery are you entitled to the jackpot?
If these tests were on regulations and procedures, no wonder they need you to pass them. They don't want some underwriter approving loans when they shouldn't have been if they knew the procedures. Especially with the current financial situation.
You passed 4 of the 6 tests. So the "bad test taker" excuse is probably just that an EXCUSE. In that you are probably not a bad test taker, and it could just as easily be that you didn't know the material. I can guarantee you that they had more than a few people applying for the same job, and would be able to pass all of the tests.
While your situation is unfortunate. What makes you special over every other person who has a wife(or husband) and a family that is also looking for a job? Does the number of kids you have give you special bonus points in applying for a job? If not then why even bring that into this report?