Is there a solvent that will lift the caulking without damaging the acrylic finish??
I don’t know of any solvent for that task but I wouldn’t take that to mean there isn’t one. I have removed old caulk from a fiberglass tub using a razorblade, the kind with only one sharp edge that is generally meant to fit into a holder. With a little care you can slice off the caulk without scratching to tub surface. If you were having trouble with that you might hold a wide bladed putty knife up to the caulk seam and cover to tub edge beneath your razor. After you cut away the bulk of the caulk you can remove any remainder by scratching with a fingernail.
They sell a blue goo in a large toothpastelike tube at Home Depot that you can apply to old caulking. Leave it on overnight to soften it up. I can’t vouch for how well it works, but a friend used it and didn’t complain. Her tub, however was enamel. I don’t know if using it on an acrylic tub is contraindicated
Denatured alcohol will soften it a bit, but the razor is the easist way. Test the finish in the most hidden spot the tub has before using ANY solvent, though…
Using the razor blade, get under one end of it and then pull it up. It’ll break in several places, but then you just do it again. Be very careful not to scratch the finish.