My husband got a 3rd and has a decent job in business. Once he's got his first skilled job no one will care after that. A 2.2 is fine. Even some grad schemes will accept someone with a 2.2.
The problem IMO is that you need more than just a degree to get a decent job - and a lot of kids don't realise this and don't have parents to tell them as they're not aware either. There are a zillion people with a degree so you need to find a way to stand out and have been involved in running a society, having a part time job, doing volunteer work - all that sort of thing to make you stand out. You did him a huge disservice IMO by giving him loads of money at uni so he didn't have to have a part time job.
He now needs help and support with turning this all around and working out how he moves on from here. He's already has a job and is working hard so that a good first step. Much better than worrying about whether he's taking advantage would be to help him work out how he gets from here to where he wants to be. He needs to keep the labouring but look at getting some more relevant experience, maybe doing some volunteering. Anything to fill up a CV.
Then he needs to big himself up - what soft skills is he learning from labouring. Team work, communication skills, problem solving, attention to detail, time management etc - with really good examples. What did he learn from his uni course, what was his final project/dissertation on. Can he do any online courses to improve his knowledge on whatever he wants to do. He also needs to be well prepared for interview, he needs to dress well, research the company he's applying to and practice the sort of questions he might be asked. He needs to be prepared to answer in the STAR format and have really good examples of the things they might ask him about - teamwork, leadership, problem solving, dealing with issues, why this job, why this company, what's he going to bring to the job etc
What does he want to do OP?