Given that he has 88, his best decision is to hit and he expects to lose -$41.

What you propose is to buy an 8 from him. Now I did the EV for all the possible cards you could be dealt with the 8 and you have an EV of about +$15 for each 8. Splitting was given an EV of +$25, so I didn't do something exactly right - I would expect the EV of each 8 to be $12.50...whatever. These numbers include the possibility of doubling/resplitting/etc.

So my question is why would you offer him a chance to go from -$41 to +$15 himself? I suggest instead to buy his bet for $50, then you front your own $100 to split. You expect to get back $15 on the $100 you invest and $65 on his $100 (which cost you $50).

These numbers are only as good as my own knowledge and this website I found:
Hand Equity