If you want (non-nuclear) explosives, BDArmory has warheads. You can probably tweak the default warheads to increase power to atomic weapon levels. You could also use the BDA missile guidance system for MIRVs.
Mechjeb helps you learn how to play the game. I must have watched Mechjeb do an orbital rendezvous fifty times before I got my own correct, but I never would have gotten my own rendezvous correct without MJ.
I may be able to help, if I can find my old SSTOs. Unfortunately, all my fighters carry kerbombs, so it's hard to fly them effectively without killing a lot of Kerbals.