What is it with left boobs @Browniee!
DD has days when she goes off it completely in cross cradle but will go for it i half rugby ball/scoop her half sitting under my arm. It’s my sole pumper though, never get anything out of my right one so I feed more from my right and express from my left every other day or so to build a stash or so DH can give her a bottle. I have a friend with an older baby who’s also a lefty refuser.
OP, you’re giving him your milk whether you express or feed him direct and lots of people do that, it’s hard work but so worth it if it’s working for you both. I’m not any sort of expert, we’re all making it up as we go along! Hopefully your local supporter can help you. Can you leave her a message and ask to see her Wednesday? Is there a breastfeeding support group near you? I don’t know if I’d stop all bottles because it might stress you out and you’ll feel better knowing he’s getting enough. Having him latch is a massive tick, he’s so tiny and sounds like he’s doing amazingly well. You’re keeping your supply up by expressing and have plenty of milk so it’s not going to go away. If you feel comfy doing so I’d keep offering him the breast, don’t panic if he fusses, and give him a bottle if he won’t feed? I don’t know I’m afraid, sorry
Or give him a bit from a bottle so he’s not too hungry and then switch to the breast? When DDs off lefty I often feed from the right and when she’s getting full and dopey I do a crafty switcheroo and she doesn’t notice.
There’s a thread on here on breastfeeding in antenatal I think. You could also try Can I breastfeed in it support group on Facebook and the Kellymom website which is packed with useful stuff and might address moving from bottles to breast. I’ll have a look in a sec and post a link if I find anything.
DP can best help by keeping you fed and watered, bringing you pillows and muslins and reminding you what a wonderful job you’re doing 
My DH has DC from his previous relationship who were ff and didn’t know much about bf but has taken great pride in being my chief cheerleader and leaving me snacks around the house so wherever I land to feed I can eat, filling up my water bottle and always having a muslin to hand to chuck me. He pokes her michelin man thighs and tells me I’ve made it happen and he’s right. She was a tiny skinny thing to start with and it’s a bit emotional how fat she’s got!
Your milk is at its best at night so you might want to feed from the breast at night and your DP can still help by changing DS nappy or keeping you company.