You will need to disassemble the board's unified cooling and inspect both the block and the acrylic fascia since the cracks you've outlined are akin to what we see on an over torqued fitting coupled together with hot coolant producing stress fractures on acrylic, which isn't good for the acrylic in the long run.
Also from the image I can deduce that the high temp caused the coolant you were using to cake/build up around the finned area of the CPU block. The heat caused the coolant to denature(for lack of a better word). I'd also inspect the pump, see if it's needing replacement and if the rest of your loop is clogged up.
I have my reservations with using sealant in that scenario, not when you have a processor that might tamper with the sealant and the material that the fascia is built around. Considering that we're into the 12th Gen for Intel's processors, I doubt you're going to get a cheap replacement for
the board's waterblock.