Ooh no dont beat yourself up! All you have been doing is comforting your child its definatley not something to be mad at yourself for!
Yes, don't be mad at yourself for giving support.
Tbh i dont know how to handle the prop situation. It might be an idea to post in props and see if you can get advice there.
Erm, I don't think we have a props board any longer.
The finger prop - do you have a key phrase? I think that's what I would do. I'd replace the finger with a key phrase "I'm here, you're okay" by introducing it whilst you have your finger on him and then lift, say, put back, say, lift say, put back say. Over a few days (not long) you can wean a prop. The verbal reassurance is lessened by saying it less frequently and from further away (also out of the room). For example on SA type things as well as helping my DS with a hand on him or similar I have also judged when enough is enough...when actually he needs to be told to go to sleep. He is not in danger I am not ignoring him but it is time to go to sleep and you don't need a finger on you because I am still responding to you. Know what I mean?
The screaming - sorry I am not sure what to suggest. Does he recover relatively quickly? some can scream every wake up but recover well. Mine would scream on waking if he had an UT nap because he couldn't transition and was still tired or because he was teething. Our entire year from 1yo to 2yo was teething - almost permanently. Drove me nuts.
Is it set nap regardless of WU time in the mornings?
I would yes. It's the fastest way to get LO to self regulate the sleep.