Hi Jake, think I remember you from a ttc while bfing thread (although have NC'd since). Sorry to hear you've had no success.
I totally understand and sympathise and felt exactly the same as you do when we were ttc number 2 (DD is 15wo and currently asleep with my nipple in her mouth - we've come a full cycle!)
We decided to give it until DS was 2 before making any drastic decisions, so at least then he will have had two full years of the benefit if bfing. You've already made that, which is amazing. Congratulations and well done.
In the end I got pg before then (not sure how, had crazy short LP, just lucky I guess). But we decided to try and wean as I really didn't fancy tandem feeding. We started with night feeds, as I was so knackered from the pregnancy, and followed the jay Gordon method when I was about 12weeks (which I'm sure you've read about already). It really wasn't as bad as I thought it'd be. We had probably 3 or 4 bad nights, but they weren't terrible - prob about 40 minutes crying each night in total. I liked it because it didn't involve leaving him on his own, I could still cuddle him and provide comfort. We also didn't have to give up co-sleeping, which we all love so that was also a bonus (although DH is currently co-sleeping with him in another room as dd and I are hogging our bed!)
I too have zero tolerance for crying and am a 'mollycoddle til I die' kinda mum. But once I had done one night I was kind of motivated to continue, as I felt I couldn't put him through it all for nothing. Also, the consequence of not weaning before DD's arrival would be too harsh, as I knew I wouldn't hack tandem feeding and weaning after her arrival would almost certainly not help sibling bonding. So try and hold in your mind the long term benefits of weaning him, when he's crying his heart out for the boob. You're doing it to give him a sibling, which will ultimately benefit him hugely.
The other good thing about the method we chose was that it was incremental, lots of small changes rather than everything changing at once. It felt manageable and at every step, I could feel it getting easier.
Once we got the wakings sorted (he still woke/wakes but is happy with just a cuddle/pat now), we got DH to start putting him to bed with stories whispered in the dark. That was insultingly easy, quite frankly, and I was annoyed we hadn't really tried it before, as I just assumed he'd kick off!
I'm wittering now, but hope it's helpful. Good luck and feel free to pm me or post here if you'd like to know more.