"Monday I am planning to leave him and go home for the hour. I think I have struggled with it as much as DS has to be honest and I feel better sat in the reception."
OP this rings alarm bells with me. To be honest (having read your posts) you sound rather passive aggressive, and more than a bit of a martyr. It's perfectly acceptable (and actually sensible) to leave your DS at nursery...yes, even if he's upset. I speak as a Mum of a DD2 who howled dramatically every time I dropped her off. Then one time I popped back in 20 minutes later, to drop off her bag which I'd forgotten, and she was perfectly contented playing with some plastic dinosaurs (the little Madam).
There is really no need for you to sit in Reception, wringing your hands, and leaving him there for only an hour is really neither here nor there. He doesn't get any chance to really get into the whole experience.
You describe him as 'your little buddy' and I think you are depending on him too much to give you, and your day some structure and meaning. You need to leave him at nursery for a decent amount of time and invest some time in making a bit of a life for yourself.
It isn't your DH's fault that you haven't made any friends locally, and so will feel lonely while he's away. It's not up to him to create a life for you there.
It's very unfair, and rather passive aggressive to agree to him going away for this trip while secretly hoping he will read your mind, and realise you aren't happy with it FGS. You have already been pregnant once, so know how tired it can make you - and it doesn't take a rocket science to know that 2nd pregnancy + toddler = even more tired, does it??? Come on...
And, if he's going to Canada, then it's just silly to only go for a few days, because the cost of the flights is a big part of the overall cost.
You have handled this whole scenario is such a silly, frustrating way and there was no need for any of it. You need to start acting like an adult and be far more direct and sensible in how you behave. Otherwise, you are going to have the sort of marriage where petty frustrations, resentment, and pointless game playing rules the day.
So you need a game plan...
a) stop fannying about waiting at nursery, counting the minutes until it's over. It's doing no one any good. Drop him off, and go home or go out for a few hours.
b) Use your free time to do something you enjoy, which hopefully will allow you to meet/make friends locally. Your DS is your child not 'your little buddy'. You need adult friends and adult socialising.
c) Stop trying to spoil your DH's trip before he even goes. It will only make the situation even worse, I promise you.
d) Make it very clear that when he gets back you will be treating yourself to some time off too.
I hope I don't sound too harsh, but I am much older than you, have been around the block more than once, and have witnessed too many people make silly school girl errors, which lead to pretty unhappy lives and marriages.