Keep calm and don't panic
Structurally meaning will the silicon hold the panels together, the tank should be fine. The biggest worry, is there a hairline crack which will grow over time. However the tank may leak and clearly that is a problem.
The issue is, it will be difficult to patch up as silicone will not adhere to cured silicone. But if you were already going to reseal it, no worries about the old silicone.
I would reseal the tank with black silicone. Go to your local Grainger and buy some 1" aluminum angle stock. Silicone this on the outside corner of the tank, I would do both front corners. Paint it the same color as the wood trim. On the inside, add extra silicone around the chip area. I would embed some fiberglass drywall tape into the silicone. Then cut a small piece of the aluminum and stick into the corner chip area. Cover it with more silicone.
If you tape it off to get clean lines and use black silicone, it should look OK. After you repaired the tank, find a place where it cannot cause any damage and fill it up. Let it set for a month or two.
Don't give up, you may be able to salvage this tank! Come on, you "repaired my hydronic heat system that could actually explode my house", you can fix this tank! This is an old school tank, adding corner frames kind of fits the tank.
On sumps, I show you mine if you do the same 🙂
I am not an expert on sump, if I was I would not have to keep rebuilding them 🙂 But I can help on what not to do with sumps. I will post a video of this sump running tomorrow.
You can do this!!!