I thought Raul is supposed to be the best technician in NV and I remember him from prior games having 100% Repair. Maybe I remember it wrong but is Raul supposed to have "only" 95% Repair? Can I raise it to 100% somehow. I tried giving him a Vault suit with +5 Repair, by reverse pickpocketing, but he won't put it on.

Followers will not equip gear that gives them lower stats (damage reduction in this case) than what they are wearing. You would have to find armor that has a repair buff and better DPS. Search the Fallout Vault wiki for what you would need.

His default clothing already has the repair buff, and a DT of 10, so it's pretty good actually.

http://fallout.wikia.com/wiki/Raul%27s_Petro-Chico_jumpsuit

However, if you did Old School Ghoul, then one of his armors has no Repair Buff, so that could be why he is at 95% now

http://fallout.wikia.com/wiki/Raul_armor

His other armor he gets if you make the other choice does have the repair buff, but no real increase in stats, so not sure why it says it's armored......

Is Raul's skill relative to the PCs level? I'm level 20 now and Raul's Repair skill has risen from 95% to 99%.