1. Means nothing.
2. Yes, you definitely need a P1, the 155 check is them kicking the tyres.
3. Not unsurprising for a niche model.
4. What?! Surely the contract you signed had the monthly payment on there, which cannot have changed since the deal was agreed? If it did, and you then signed it, well 1) that's very silly and 2) get it changed NOW. Financial Ombudsman if you must. Actual interest rate means nothing really, it's the actual sum you're paying that's important.