Thank you for the reply.

M has done a 12 hour night maybe 3x in his entire life.

He is definitely low sleep needs and was fighting bt every night with a nap, which is why we dropped it. Honestly, he was doing well with 11 hours for a while. But maybe he is growing or more active and needs more sleep. I agree with you, that he is OT. When he was at the baby sitter's, she did let him sleep. The problem for us is, he doesn't sleep here. He screams and fights the whole time. Sometimes, I can get him to nap when he gets to this point and then when I let him nap, his night is even shorter. So I don't even know what to aim for when I let him nap.
We really do try for an early bt and the screaming goes on for ages. Every night is a struggle. We started the battle at 5:30 the other night and it went on until almost 7. So yes, we can do early bts, but it doesn't end up being an early bt because of the fight.
We also found that he doesn't tack on sleep. When we were aiming for 6 and he actually went to bed at 6, he woke at 5. 11 hours seemed to be his max. So we always aimed for 7 to at least get a 6 wake up.
Sorry, I am not trying to be resistant to suggestions. He is just so frustrating and always has been when it comes to sleep. He seems to do exactly what he is not supposed to do at all times.