to me it sounds like you have the following issues and this is how id handle them if it were my truck:
1.i would get the the injectors pop tested locally (not from where you bought them.second opinions don't hurt.)
2.you should of left the timing be.at 8 BTDC the truck should never smoke white nor be hard to start due to timing.im not saying it may not be optimal (in my opinion it is close enough though.) im just saying you should never experience any issues,related to timing at 8* BTDC.
3.you should check your glow plug system and #1 could be the reason for hard starting as well.
4.you should turn your fuel screw down.black smoke results in poor economy,isn't any good for the environment,does nothing for performance and results in high EGT's.
5.lower your focus on engine timing being you main cause for concern.it isn't.