While you have access, do the starter clutch rollers, springs and pins. The starter clutch is working fine as has been mentioned, only supposed to turn in one direction. Very little oil gets to the starter clutch area, and it does not have a good amount of flow and can be there for some time causing the rollers to stick and the springs (similar to a ball point pen in size and strength) as well.
Now that you have the engine turning over, just a matter of being methodical and getting it back in the bike.
I also agree, starter is probably an issue. There are posts on this and GWDocs on how to rebuild a starter. Give a look, can't hurt to go in and have a look. You will at least be able to give it a cleaning and get rid of the 30 odd years of brush dust. When you take it apart, match mark the casings and be careful when you remove the armature.
While you have the engine out, I'd have a look at the clutch stack. After 30 odd years, never know the condition. A set of friction plates is not that expensive and you don't want to pull the engine again for a possible clutch issue. Not much else in there you would have to contend with. This recommendation is predicated on the possibility of keeping and riding the bike.
Don't get discouraged, it's similar to an older car, lots of issues that need to be addressed one at a time. Good luck.