Can you get gas at the BJs in Stoneham?

Yes

Thats the ONLY place I gas up now! .10 off with card. Also each month (lately) they have on the front page a brand of products where if you buy 2 you get .25 off with a BJ's Perks credit card

Only with a membership.

Yes. Often really below every other local gas station's price. And sometimes they ran special discounts if you buy specific items at the BJ store.