I’m wondering exactly what has been done to my poor tub, and what I can do to fix it. The be previously removed the caulk and replaced it on the bottom of the board, but I didn’t add enough caulk to fill the large gaps, especially towards the back of the tub. I’m wondering if I can rip the wood off, and what it’s hiding? Also what I would need to do once ripping it off to have a cleanly caulked tub. Or maybe I don’t rip it off? I’m completely clueless. Thanks in advance.
If somebody thought that was an improvement over the underlying joint, then I wince at the thought of what's underneath it. It looks like he used ALEX caulk instead of a class 25 caulk like 100% silicone, so movement of the tub cracked the caulk.
Removing the trim may be a lot like turning on the light in a bathroom with roaches. You won't get to unsee what's under there. If the wall is significantly damaged and sprouting mushrooms, you may end up removing and replacing the wall liner. Not ready for a significant project? Best to clean up the lower joint with plastic tools (to avoid scratching the tub), and then you would apply a bathroom sealant like the previously mentioned 100% silicone. The "class 25" part means that the sealant can move 25% without cracking or debonding, so if you use a silicone alternative, it too should be qualified as "class 25." Higher classes, e.g. "class 50," are better still.
A class 25 sealant isn't sufficient, though. It should be designed for use in bathrooms to minimize mold growth potential. I always use 100% silicone if you couldn't already tell.
Ready for a significant project? Then remove that trim and be prepared to deal with a ghastly horror show. Try to use soft tools (like a plastic putty knife) to avoid damaging surfaces.
At this point all we can do is guess. My guess is that the wall, drywall, was damaged and covered up by the wood strip. You won't know until you remove it. If you do remove it and the damage isn't bad and the moisture hasn't rotted the studs, you could replace the wood with a tile border all the way around the tub. If there's extensive damage, removing the wall upward until the damage is cleared would be required. Replace the drywall with cement board and add tile.
That is a highly unusual installation. My guess is that the tub surround was either broken or installed too high.
Wood in a tub/shower area is a recipe for disaster. I would consider removing it and seeing what is behind it and go from there.
You might able to just apply new caulking from the tub surround to the tub or it might need more extensive work. The only way to find out is to remove it. You can always ask another question once you get it taken off and have more information.