Hi OP, I have been directed here as my DT1 is similar to your ds. Except I'm not pregnant, and only work 2 days- definitely affected by tiredness though.
My Dt1 has reflux, which was only starting to be properly identified at 11 months, and only on enough treatment via a paediatrician at 15 months. he vomits within 2 minutes too, reliably, and can't stop til he's emptied his tummy. It's making any form of sleep training really difficult. That plus bedtime being hectic with him, his twin, and their 18 months older 3 y.o. sister. He's better in a travel cot than a cot, but when he wakes around 10-11 he does come straight into bed with me. It's only very recently got me any more sleep though, and that's with adding a bed guard for my reassurance after multiple fall outs, no DH in there, and having finally, finally night weaned at 17 months (from 3-4 bf a night). I think we may try the big boy bed, gradual retreat again.
I would like to add that my dd, at this age, was a nightmare. She'd slept through from about 3-4 months to about 13 months, bar teething etc, and self settled from 9 months. I was heavily pregnant with the dts, working, miserable. I was taking up to 3 hours to get her to sleep at night (with gradual retreat), then she could wake at midnight and I couldn't get her to sleep til eg 5am. Absolute disaster. I did sometimes panic about wtaf we'd do with two new babies to manage too. However, for her, the sleeping changed dramatically as soon as the boys were home from hospital (in 4 days, more as DH had a wierd illness where he just avoided being admitted himself and my cs recovery than them). Literally stopped waking for hours in the night on night 3 of the boys being home. I'd say 4-6 weeks of decreasing time with the gradual retreat, and by the time the boys were 2 months old she was sleeping well after 6-7 months of Sleep Hell. for her, it was definitely anxiety where she knew Something Was Up but not what if that makes sense. We didn't actually end up doing anything differently. I'm just saying this to give you some hope, it will improve.
I think the big boy bed suggestions sound good. We have our terrible sleeper in a travel cot wedged against a single bed in the boxroom, so maybe we will get him his own covers and try it. Even his paediatrician suggested giving up with the cot. I ignored her as she also told me to stop bf. In fact, I've ended up stopping bf (not because of her, but i hit the wall on restricted diet for me as he is dairy, soya and egg intolerant and Dt 2 dairy intolerant). Now looks like I'll go with the bed option too 
I couldn't do cc with the vomiting, as it was too soul destroying, especially as then I'd worry about real hunger at night wakings. I have, by just refusing to rock, got Dt1 settling initially in my arms without rocking, now I'm sitting on the single bed and laying him with his head in my lap and he's going to sleep like that. Pretty slow progress, but limited here as any crying disturbs my other two from self settling and causes greater bedtime problems. I think eventually I will work up to him laying by himself to go to sleep, but tbf.I'm not making progress with that with the travel cot.
Oh, and op, I'd try anything. I understand the desperation, both from him, and dd when I was heavily pregnant too. It's grim.