Accidentally removed part of rubber strip between bathtub and glass while replacing silicone caulk

I've had moldy, leaky silicone in my shower for a while, and decided it's time to replace it. But I got over-eager in pulling it out and got a chunk of an also-moldy rubber seal/spacer/gasket that's between the tub and the metal frame. There's a picture below. Right now, I'm trying to figure out three things:

1. What's it called, anyway?

2. Should I worry about the fact that I took out a chunk of it, or just reapply silicone over the space (and maybe try to fill the space with silicone)?

3. It's pretty moldy — can it be removed or replaced without taking the glass side off?

Any thoughts that help me avoid setting myself up for future leaks would be super helpful.