You sound completely defeated. Do you EVER discipline him? Because I'm seeing no mention of it.
You need to remember - and act as - you're the one in charge NOT him. That's actually more important than what he's wearing.
Dd went through a v short phase of trying this one (iirc it lasted 30 minutes!) because like fuck would she get away with it!
He's lazy and entitled and you know it.
At this point I'd be stopping all pocket money until he behaved appropriately and appreciatively. He needs to be home at X time to eat dinner or else it's reheated in the micro or he goes without - his choice.
He wants money to spend on eating out, socialising, fancy clothes? Then he gets a bloody job! No excuses!
Dd got her first job at 14 and has worked ever since. I gave her what pocket money I could afford (also a single mum) and it was her choice to either spend or save.
In the real world some can afford designer (which is rarely much better quality than high street, just with a coveted name/logo on) and many can't. He's MORE than old enough to learn that and deal with it. You are not doing him any favours if you don't teach him this ASAP.
Dd also had friends that tried the "but I'll get bullied" line on their parents - she told me some fell for it some didn't but that it wasn't true. Just the new "but everyone else has got one" cos they know parents fret about their kids being bullied.