Hi there, welcome to BW - you are most definitely not alone

I am going to give you some links along the way to look at - they are really helpful.
First off, naps are very developmental for a lot of LO's and it takes time for them to get the hang of it. I had a really hard time understanding that babies just don't sleep when they are tired...until I read Tracy's book and learned about the different temperaments and sleep cycles. I know the short naps are discouraging just now, but they will get better. I wouldn't say you have caused the habit with the paci, because a lot of LO's have trouble transitioning. But the paci could be a sleep association and you just need to teach him to get through those jolts on his own.
At nearly 5 months the A times are like this:
5 months 2 hours - 2.25 hours
And sleep is 2x 1.5 hour naps + 45 min CN and 11 - 12 at night.
I'm actually wondering if his first A time is too long for him, he may need to go down earlier - lots of LO's need their first A to be the shortest. Have you tried 10 or 15 mins earlier? Usually 30 min naps are OT naps. Since he's still learning to transition between sleep phases, if he's OT he has a harder time and the jolts seem more abrupt.
Something you can try is also W2S - you can read how to do it here:
What is wake to sleep & holding through the jolts?also:
Short naps - why does my baby wake after 20 minutes?I would recommend the HTTJ method for your LO, along with shush/pat. So that would mean that you would have to sit with him for a lot of naps. This is totally normal when sleep training. I sat in Finn's room for most naps from weeks 12 - 20. It was a long road but it really does get better if you are consistent.
Short naps are not restorative and as a result you get an OT baby. The fact that he is sleeping through the night without issues means he is handling OT quite well. Is he Angel or Textbook?
Have a look here:
Why is it important that my baby gets more than a 45 minute nap?Why can my baby sleep great at night but struggles with naps? Some answers to your questions:
1.) Should I continue to try to persist with the nap extension techniques right up until the next feed. I got very concerned because my little guy's throat became very hoarse (he really hasn't been a crying baby) and this consistent crying seems to have worn him raw. It has had definite effect on my resolve...I just feel so bad for the little guy and don't want to do permanent damage to his little vocal cords! Sad
Generally you should persist with shush/pat for naps for at least 45 mins. Then you can get your LO up and either do some A before trying nap again or if hungry feed. You need to reduce the next A time by quite a bit and try for the next nap.
2.) What do I do if he wakes up and just stares at me? Leave the room? Stay and keep trying (basically get him upset so that I can try to get him to sleep?)
This is a bit of a tough one. If he's not crying but you sense he is tired, you can leave him to it. You do not need to use any methods while he is trying to self-soothe. This is his chance to try to do it for himself, and they quite often surprise us. You need to be able to distinguish his cries:
What’s a mantra cry?Most LO's have a mantra cry and this is their way of soothing themselves. This is a cry that doesn't need your attention.
But if he's crying to the point where you think he's not going to recover, then you need to start a method, usually shush/pat. There is lots of crying with nap training, it's normal. I am pretty sure no LO ever hurt their vocal chords :-) I was given the suggestion to get ear plugs. And it helped. It seems almost cruel but really, you need to be confident while you are training. Tracy says in the book do not feel sorry for your LO. And it's true. If you are not confident, they know it. It's best to do training when you are comfortable with crying and know that you are not hurting your LO but rather helping.
3.) How do I start weaning myself out of the equation. For the last week I have put him down and helped him fall completely asleep and stood beside the crib for 20 min to ensure that he was in a deep sleep (and then figured I'd wait the extra 10 min to see if I can help him through the jolts - what the heck). How do I start to remove myself so that I'm not the prop?
This comes in time, as they learn you will need to do it less and less.
The point is you are there for him, and teaching.
You are not a prop:
When do I use shush-pat & is it a prop? When should I move to pu/pd?.) Have I already ruined things by abandoning the nap extension attempts twice for the afternoon naps. I was so worried about his voice that I waited until he was somewhat calm and then gave up, picked him up and took him out of the room. Does he now expect that after a certain amount of crying I'll give up? The afternoon nap extensions are the most difficult. He just seems totally amped and the only time I was able to get him to sleep again it took one whole hour of PU/PD! Arhghg. The last two days getting him down for a catnap was virtually impossible. (I have accomplished it once but not been able to again).
He's amped up because he's OT. That does make it really really hard. So that's why you need to tweak the routine a bit to get him having a good AM nap, and continue to support his nap training. You haven't ruined anything, but it does pay to be consistent :-)
You are doing a great job - you are a concerned mummy who wants the best for her LO, that's the first step and right attitude - I don't think it's paranoid at all :-) The rest is just some hard work to teach him how to do it on his own.
hehe looks like Jo beat me to it ;-) It took me forever to get this posted for some reason - BW is hanging on our internet.
I realize now that you said nap extensions which Jo has said, 20 mins and then get LO up. If you are starting with shush/pat and LO hasn't slept yet, try for 45 mins to get a nap out of them.