9 months is difficult as it’s a huge sleep regression. It sounds as though he’s poorly at the moment too so it’s perfectly natural that he wants the comfort and closeness of BFing and being with you. I do understand how overwhelming that can be at times though.
as he’s portly I’d try and have a quiet day today if you can and feed him as much as he wants.
Make a plan for when he’s feeling better. You’re aiming to drop a feed every two weeks. This is to let him adjust to the new amounts he has to eat and drink and to reduce your risk of mastitis.
So maybe start with DH getting him up and going straight to breakfast and offering a cup of formula with his breakfast instead of a bottle? By 10 months he’ll only need 450 mls a day of formula and that’s if he was totally FF so you don’t need to worth too much about giving him huge bottles in the day.
I’d carry on feeding him before his two naps and before tea and bed for now, if that’s what you do.
Once he’s got used to breakfast being good and a cup of milk, I’d swap the feed before his lunch or tea for just the meal along with a cup of cup of formula and his food. Then leave it two weeks and do the same with the other meal.
So that should be about 6ish weeks and you’ll be down to feeding before the two naps and before bed and he’ll be coming up to 11 months?
Some people find that dropping the bedtime feed is easier if you go out for a few evenings, I don’t know if you want to try that and leave DH with him and a bottle?
Once he’s 12 months you can try some
gentle night weaning. This method is aimed at parents where the baby is BF but works for Combi or FF babies too.
If you want to drop the feeds more quickly you can. Some leave it a week between dropping a feed and dropping another.
I think though as he’s poorly I’d just feed him as much as he wants for now and get DH to bring you some snacks and drinks 