Hi there, sounds like you're having a pretty tough time of it.
You'll probably get lots of different sorts of advice on here but my own view (with DD2 being 6 months old at the moment) is that he needs to get into some level of routine - if he's snacking all day then he's going to be snacking all night. Ditto, if he always has a mummy to lie on then that's what he's going to choose - lie on mummy, snooze and eat whenever he feels, perfect.
Some people will undoubtedly say that at 5 months old, this is all perfectly fine and attachment parenting is great and healthy and wonderful for the little lad but it sounds like it's making you bloody miserable.
Couple of thoughts on the day time. Firstly, if he's very hungry all the time have you thought about starting him on solids? Might be a tad early, but DD2 started at 5 months and plenty of other people start then. Would enable him to go longer between meals, theoretically at least. Secondly, try holding off feeding him for an extra five minutes at a time so you can stretch the gap between his feeds a little at a time - it'll be a slow process but over a week or two, it may help stretch it so that he's only settling down to eat at much longer intervals, particularly if he's eating solids. This should also help the daytime sleep as he won't be snacking so much.
On the night time, if you do want to try and put him down at 7 and then get him to sleep longer in his own bed then (speaking as a DH) I'd get DH involved much more. Little ones crying in the evenings at night seem to stress mums much more than dads, plus dad hasn't spent all day listening to them yowl. If they're fully fed then they should be equally happy with dad as mum. Once you've put him down, if and when he starts crying let DH go in and deal with it - guess you guys can do whatever you think it needs, but be it rocking, jiggling, cuddling, let DH deal with it - if after a certain amount of time he's getting too stressed, step in for a while and carry on, then you stop and let him do it again, til DS eventually falls asleep - I guess the point is, that he doesn't need feeding so don't. Ditto through the night, when he wakes for a feed try and make sure he stays awake to take as much as possible - if he then won't settle/ wakes up 15 mins later, get DH to settle him (again, relieving him when he gets too stressed) - the point being that he isn't just fed to sleep again. I think we also found with DD2 that she settled better with me than DW because she didn't have the smell of milk under her nose tempting her all the time!
I'd say it'll obviously take quite a few nights for him to sort himself out with lots of crying from all parties, but hopefully it's a way forward that relieves the stress on your and helps the little lad sleep a bit better.