The less Ax you beat, the less you wanna shove.
Since i don't expect an unknown tag to go broke with much less than TPTK (especially since he probably repops you preflop with AK anyway) unless he has a draw to go with it, i probably wouldn't shove much lighter than A2 here.
If i have a totally different type of hand like a lone Ks it's a different problem, I'm probably going with it because i still have equity no matter what he has and i don't want to just give it up on my first steal attempt, it would lead to an awkward metagame from then on. With a lower spade it's dicey, because i might be drawing dead already so i probably wouldn't risk it.
His raise size is somewhat weird tho, i wouldn't be surprised to see him with a draw there also trying to play back cheap. Either that or you're drawing to 4 outs ♦ I'm not good enough to lay down A2 against an unknown here either way, i assumed he was a tag because of his stack but for all i know he's going nuts defending his BB with A5s.