FotF and SUS have no problems stacking because SUS will always increase the monk's unarmed damage. For example, an 11th level monk does 1d10 normally. With SUS he'd be treated as a 15th level monk and do 2d6 damage. Tacking on the two advancements from FotF would put the damage at 2d10.
Swapping it so FotF is first and then gaining SUS results in the same thing. The 11th level monk's 1d10 would go up to 2d8 from FotF, and because SUS treats the monk as 4 levels higher, using any of the levels 2d8 comes into play (16 through 19) means it'll go up to 2d10.
As for advancing past 2d10, technically there is no way to according to the Epic rules. To quote the SRD:
Unarmed Strike
The damage for a monk’s unarmed strike does not increase after 20th level.
The best thing to do from this point is to get size increases either to yourself or effectively to your unarmed strikes through Greater Mighty Wallop and other stuff. I'm pretty sure any reasonable person would just double the result from the 1d10 line.