What tyre would you recommend for a camper van?

What is the best budget camping tyre for a 5.9 metre long, Fiat Ducato based motorhome, with a 16'' wheel diameter, please ?

Will washing up liquid stop paint from sticking to my tyres?

Does washing up liquid prevent overspray on tyres fron sticking ?

Will a 16-inch rim space saver wheel be acceptable on my car with 17-inch wheels?

Will a 16-inch rim space saver be acceptable on my Mazda MX5 with 17-inch wheels?

My car tyres have been flagged as perished by an MOT. Shouldn't they last much longer than 3 years?

A recent MOT stated all four tyres are advisory items as they've perished, yet my 2018 car has only 15,900 miles on the clock and just does two or three local trips each week. Surely tyres should last...