Are you paying them all on time every month, even if only making minimums?
If so it’s probably not great, but not as bad as you think. However, it’s worse for cancelling the cards than just paying them off and leaving them open.
Not necessarily.
By canceling the cards, he locks in the account terms, including interest rates.
If those are credit cards, some issuers engage in "universal default" (if you default with any lender, you default with them, too) and predatory interest rate increases, including hikes to as high as 40% APR.