I’m in the exact same situation in South Carolina. In my experience, a stock 250 isn’t meant to fish in 30-40 ft. Fluoro is a must for that depth & really any 250 in general. If you want it to stay down that deep, I’d say adding weight is the solution. 1gram makes a noticeable difference, so something like Zappu board weights could work, or even upsizing the split rings or hooks slightly could get it down a little faster but not ruin the sink rate you want.
As for the slow straight retrieve, that’s how the bait has been to me. It definitely has a speed threshold you have to reach if you’re doing a straight retrieve. Whenever I fish them deep, I always start reeling it fairly fast to get it off the bottom & start gliding, then slow down from there.
Hope that helps