Evolved1
make sure the pudding isn't too soggy but that just ruins everything
I know the feeling. Have gone through the game on Amateur, Normal, and Pro, bought infinite grenade launcher and assault rifle (and nothing else but relevant skills) and am still short around the same you are. Terrible at Mercs too so that isn't a viable option for me and I really don't want to grind Chris 5 for it. Not nearly enough skill points awarding throughout the game, you should get some for completing a chapter and not just the ones you collect throughout.
mercs is really the best way to do it, imo... you don't have to be very good. just get a little bit of time at the beginning and let it expire as things get too tough for you. If things get *really* tough and you still have a bit of time left, just run away until it expires.
even lame early enemies will sometimes drop skill points. idk if item drop affects skill point drops, but you could look into that as an option. either way i think skill points are best collected in mercs. and it's not quite as boring as sp grinding.