Noooooo! That's way too much, and he won't see the invisible spending that keeps the household afloat, will he?
I'd be inclined to have a grown up birds-and-bees type financial talk and show him the full finances. Show him what goes out in rent/mortgage, utilities, council tax, house insurance, internet/phone, any subscriptions, for starters and ask him to consider what his share of that for keeping him warm, dry, clean, entertained and out of the weather and off the streets might amount to. He's old enough.
Then take him on the weekly shop and have him total up the spend as you go. As he helps put it all away, have him note all the things that are exclusively for him (lynx?!) to use, eat or drink.
Then have him keep track of what money actually goes through his hands and yours for him on lunches, fares, school clothes, trips, phone contract, shoes, etc etc.
If all that doesn't exceed what your ex is paying, I'd be surprised! Show him where the money comes in from, too: your earnings and your ex's contributions, any other income.
If there really is a surplus from his father, discuss with DS what he might need money for later and set up a savings account for him which you pay into. Youngsters can have tax-free ISA accounts. If he goes to uni later he will be very glad of a nice lump sum. If he gets in the habit of having big wodges of cash to spend every month he may get into spendthrift ways and find it hard to manage later. He has what - two more years of ex's contributions?
He should start to prepare for when that tap turns off. Nobody has to pay a penny towards his support once he's an adult! You might, but you don't have to, not unless he's studying full time.
Does he even know this?