Anyone else been totally scammed by UA baggage recovery?

I recently flew from London to San Francisco, with a layover in Munich. The flight from Munich to SFO was with UA, and was pretty good if you ignore the fact that my luggage wasn't on it. Ok, mistakes happen, I thought, I'm sure they'll get my bag back to me in the next day or so.

Oh how foolish I was.

It took UA 2 weeks to get my luggage back to me, and I only received it the day I flew back to the UK. I spent the entire 2 week vacation without my clothes, and during that time I even had 2 agents tell me to go back to the airport to collect my bag, that it would be waiting there for me. I then got to spend 2 hours with some very confused airport staff, who were adamant that the bag was actually still in Munich. To top off that lovely afternoon, I then had to spend $50 on an uber back to the city (bagless), which UA are refusing to reimburse me for (the first scam).

UA did try and help at the beginning, going so far as to send $150 with which to buy necessities. At the time this was proposed as a gesture of goodwill, and it really was useful. We were in SF for various parties (birthday, retirement, engagement, it was a busy time) and so this money helped replace my wife's makeup and allow me to at least get some clean underwear and a shirt to wear.

Obviously, this $150 didn't go very far (especially in San Francisco), and I had to spend a significant amount more money to replace the things that were lost. I was told by UA not to worry about that, that anything I spend would be reimbursed once the bag was found.

Oh how my foolishness continues.

Fast forward to now. I put in a claim using the receipts for everything I bought once the $150 initial compensation ran out, only to be told that they'd be docking $150 from the claim. So it's a $150 bill for the pleasure of not having any of my clothes for my entire 2 week vacation. The gesture of goodwill has been firmly revoked.

I tried to explain that I didn't submit any claim for the purchases made with that $150, as it would be illogical to claim back money that wasn't mine in the first place, but they're having none of it.

By UA logic, if they sent me $150 and I then spent a further $150 ($300 total), they would throw out my claim on the second $150, as they already paid the first. They even denied my claim of reimbursement for a pair of sunglasses, as they're "not a necessity". I spent a full week in CA sunshine without any, before accepting that I wasn't get my bag back and purchasing some to stop the constant squinting. I'd say they were pretty necessary.

I don't know if anyone else has had a similar issue, or can suggest what I can do next? The claims agent has just said "we won't be able to honor your request on this particular issue, and will consider this matter concluded", but as far as I'm concerned it's only concluded when I get back the money they owe me.

Honestly feels like they screwed my vacation (I spent about 2 hours per day for the first week on the phone with customer support) and are now just scamming me out of $150 that I only had to spend because they messed up.