Sorry for the delay - I can't type much on my phone so had to wait til I could get on the laptop to reply. Hugs for what you have to come! I was sleep training my littlest one when my daughter was 3ish, and she never once woke, if that helps. I'm sure you'll be fine - a bad night or two and you'll be there, I'm sure
For your questions...
1. I probably would wean the swaddle at the same time - you might as well, or you'll have to do it all again shortly anyway. I don't know what you think about sleeping bags but I always found them to be an easy step on from swaddling.
2. I would put him into bed and then walk out. If / when he starts to cry, that's when I'd go in, try and settle him in the cot, and sit with him. If he doesn't cry, or is just moaning, I'd leave him to it. If you need to go, you can put your hand on his back to settle him (or you could even start with having your arms around him like you're holding him, while he's in the cot if you think that'd help), that's fine, but try not to have it there when he goes to sleep. If he needs it, that's OK too, just plan your next step the next day to have him go to sleep without your hand being on him (e.g. use your hand to settle him, then move it to the mattress / bars of the cot once he's calm). Then after a day or so, try and just use your voice and sit next to him. next day, just use your voice and sit a bit further away etc. til you are settling from the door, then outside it, and then you're done!
3. Yes, definitely stay consistent - it'll be over quicker if you are. I know it's hard - we used to have 2hr NWs with my son and it was horrible - but if you stay consistent it's easier on you both in the long run.
4. We had EWs too.. I feel your pain. What I did was have an acceptable WU time in mind (e.g 6am), an treated everything before this as a NW. Yes, we did sometimes start the day at 4.30am, but for an hour and a half of that I was doing WIWO. That said, if you think he might genuinely be hungry then I would feed, but try and make sure he goes back down awake, so you're not introducing a feed-to-sleep association. Then walk out, and go back in to do GW if he needs it.
5. You could start with stopping the hold-to-sleep association first, and keep the feeds if you think he still genuinely needs them. You might find that if he learns to self settle then he wakes less for a feed anyway. Just make sure he's going back in the cot awake. In the meantime, you could try upping his calories in the day. Have you tried feeding in a quiet, dark room during the day, so there are less distractions? I had to do this with my daughter, who was very nosy! Or you could increase the amount of solids he's having? Offer a snack before bed? Or have you tried a dream feed at 10.30ish?
6. I think it's quite common to sort nights and then have nap problems
If that happens, it's probably cos he's getting more night sleep and therefore needs a bit of an A time push. I would try for a nap for 30 - 45 minutes, yes, then go and do something else for 10 minutes (nappy change / feed / snack / look at books), then come back to it. If he'll sleep in the car, I'd do that if he really won't nap, and then the next day try increasing his first A time by 15 minutes and see if that helps. Just don't AP by holding him or you'll confuse him...
If you're going back to work in 2 months I'd say this is the perfect time
It'll be much easier to do it now, and gives it plenty of time to bed in before that becomes another factor! How many days a week will he be in daycare? Would you do set naps at home? Many LOs do well on set naps from this age. Or otherwise you might just have to do catch up days at home if he doesn't nap well at nursery. Either way, if he's sleeping independently and you have an idea of what A times he needs it'll help him catch up / deal with the change I reckon.
Finally, on the singing, I used to sing to Jack when he cried to help settle him (in fact I still do if he's really worked up about something). A bit like the hand on the back, I'd just make sure you're not singing right until he's asleep. Once he starts calming himself I'd start slowly singing quieter and quieter until you've stopped. That worked fine for us.
Good luck!