I will let the boss explain, answer #2:
https://www.moyermarineforum.com/for...19&postcount=2
All your head bolts but one should end up in the water jacket. So if you see something at the bottom, it should not be there. Based on previous discussions, I would assume that your studs are not broken, just very corroded from being in contact with salty water, and what you think could be the bottom of a broken stud, is just solidified crude/goo/rust.
I would recommend first to take a screw driver and a hammer, and bang whatever is at the bottom of those holes. 90% chance you will go through that bottom crap and end up in the water jacket