Class growths for fe1 are 100% hp and 50% in everything else sans resistance. But they're not really chances, they're more like counters. Every time a total of +1 is achieved, the stat gets +1. So with a base of 5 strength, the class would have 6 strength at lv3, 7 strength at lv5 and so on.
For promotion gains, they don't exist. The only thing that happens is that, if the stat of the unit is lower than the base stat of the class it promotes to, the stat rises to the base of the class. So if the promoted class had base 12 strength, and the unit itself would have 8 strength when he promotes, he will have 12 strength when he's promoted.
Pretty much the same as with fe2, iirc.
Just because I'm not interested in the games much anymore doesn't mean I cannot help out :P
Oh, and please correct me if I'm wrong. This is just from the top off my head.