Sounds a lot more confusing than it should be, the only major problem I can see is that he expects another 2 years of payments to even it out, but at the end he's explicitly said that he will own the car and do with it how he please after that?
Some figures would help explain the situation easier I think.
As an example, assuming the car was £600 a month (£14,400 over two years), he's paid that for 2 years with your contribution (so he's paid £450 a month equalling £10,800), and says you need to keep paying him for another 2 years until you're at the same, so you've been paying him £150 a month for 2 years (£3,600), and wants you to keep paying that for another 2 years (£3,600), 4 years in total, to get you to half what he's paid for the car already (£7,200)?
So for in order for him to be saying, you need to be paying for another 2 years, you had to have been paying around a quarter of what he was paying? So if your payments were separate and in addition to all the running costs you're paying, then if he sold the car now, you should expect 25% of the value left over in any normal situation, but this doesn't sound very normal.