How much jail time for using a stolen credit card?

This depends on the exact charges, the facts, and his prior record.

Depends on how he is charged. He can be charged with each time he used the cards, or he could be charged with theft for a total. It also depends on his criminal history. He is looking at prison, not jail time.

He is facing as little as zero time to quite a bit of time. It's unclear whether he took several cards from one wallet or the several cards were taken at separate times from separate wallets. This impacts the number of counts he may face. Each use of a card can also be filed as a separate charge. And it is possible, though the facts are presently provided, that other charges could be laid? Your boyfriend should seek advice on his specific circumstances from a qualified criminal defense attorney at his first opportunity. If he cannot afford counsel and has already been charged, he can seek to have the court appoint counsel for him.

It really depends. Does he have any priors? If this is his first offense he may be able to work a deal where he pays restitution in exchange for a dismissal.