I'm sure this is very difficult. Kicking him out didn't work for long (because his girlfriend wasn't truthful). So she's as manipulative as your son is.
Did something traumatic happen to your son? A devastating event, an accident, some sort of drug activity? Anything that could cause a major psychological break or a fear or massive depression? Does he have a mental illness? Or has this been building for some time and you just hoped he'd outgrow it or get sick of it? If the former, he needs treatment. If he's violent or a danger to himself, you need to take action to have him contained in a facility. That's tough to do, I know, and it may not be justified if he's not that dangerous or unbalanced. If the latter, then perhaps his laziness has been enabled by you and your husband, and you've just finally reached your limit. That's tough on your son because he has a lot of reasons to think this behavior is acceptable - annoying, but acceptable. So kicking him out seems shocking to him.
If you're going to do it, do it. But you tried it and then relented (telling him "it's fine"), so if that's going to happen again, it's going to be fruitless to attempt what you will not finish.
If you cannot bear to kick him out because it's harder for you (and that may be what this about - making YOU comfortable), I would only demand what you can truly make happen. So, saying something like "You have to get up by 7 a.m. and help around the house" or "You have to get a job" are not enforceable by you. You can wake him but you will give yourself a headache, and you cannot physically lift him up out of the bed or take him on an interview.
However, how is he doing stuff on Instagram if he doesn't have a phone or a computer? You are providing this, right? So stop. Don't say it's punishment - say that you cannot afford it and also pay his expenses like food and utilities (I assume he's using hot water and electricity). Unless you're going to lock up the soap, shampoo and laundry detergent, he's going to use those as well. So, stop with the luxuries. Stop paying for his phone/computer - if there's a chance he'll get a job, get him a cheap flip phone (no data, no games) with a very limited plan. He can receive/make calls related to job prospects, but if he just calls his girlfriend and runs out on the 14th of the month and has 2 weeks to go, oh well.
Does he have a car? Who's paying for that - payments, insurance, excise tax, maintenance? Is it in his name? If not, you can sell it. If it is, you can stop payments and let it be repossessed or let the insurance lapse. Again, you say you cannot afford it because you're already paying his living expenses. You've raised him, it's time for him to leave the nest and be responsible for himself.
So if he comes home to lie around, he doesn't need special stuff. It has to be totally spartan. That means you change the Wifi password and don't write it down someplace he can find it. Don't use your birthday or anniversary or anything else he can figure out. Does he use your car? Does he take your money/credit cards. Or is he likely to? Then have your statements sent to a post office box, lock up your wallets and the car keys as soon as you come in the house in a safe you can buy for under $150 at any office supply store. Put any valuable documents in there if you don't have a safety deposit box. That includes anything like stock certificates. Put your jewelry in there - anything he could pawn. Take him off the car insurance if he's on it. Cut back your cable TV channels (and yes, I know it's a hardship for you) so he has nothing but the basic networks. Or, change your passwords for premium things like Netflix if you can.
Does he demand that you cook, or demand certain foods? Stop that immediately. He can eat oatmeal for breakfast and peanut butter/jelly for lunch, your leftovers for dinner. No ice cream, no cookies, no filet mignon. If you have to lock up your own snacks in your room, do it. Is it dramatic? Absolutely. It's a pain in the neck? No question. But his conditions have to be bare sustenance and nothing else.
If his room is a mess, close the door. Put a laundry basket in there and do not wash his clothes. If he puts his stuff in the hamper with yours, separate it out. If he says anything, you say, "I don't know how your stuff got mixed up with ours, but I'm sure it was an oversight. I know you wouldn't expect me to do your laundry."
Don't drive him anywhere unless it's the employment office or his doctor. Say you don't have time or money for gas.
If he gets the message and gets a job, fantastic. He can start paying for some stuff. If he just uses it for his own social life, you'll be no better off than you are now. If he gets up and mows the lawn, runs the vacuum and washes the dishes, you can see if that continues for a week. Even so, it's not covering the mortgage and the heating oil.
You and your husband have to be absolutely in sync on this. If your son abuses you verbally, get in the car and leave. If he's out of control, call the police and say you are afraid of your son. They will take him and let him spend the night at taxpayer-funded accommodations downtown at the precinct.
I don't know how strong your backbone is.