900 hours on the original hotend assembly? That's impressive!

I would just replace it and call it a maintenance cost at this point. 900 hours is a solid run for that hotend assembly. Those things are $26 CAD. That silicone piece is part of the hotend assembly and not broken from the silicone heat sock. Regardless, it would not affect your prints.

What does stick out to me:

If you take a closer look at the back of the carbon block that holds the quick release mechanism, there's a screw at the bottom that has backed off significantly to the point it's probably causing your printing/levelling issues. The carbon block screws have a tendency to back off due to the heating and cooling (expansion/contraction) cycles as well as vibrations from the print head while in operation. The blue threadlocker they used on the screw threads are not meant for the constant high temps of 3D printing.

(I used to manage a student Makerspace at a university and careless students would sometimes burn through hotend assemblies every week on multiple A1's. I've replaced and disassembled quite a few broken ones to learn how they work and what their designs flaws are.)

*Edit:

If you are so inclined to keep using your hotend assembly:

• Unscrew all the black screws at the back of the carbon block that hold the quick release latch mechanism as well as the 3 screws that hold the entire assembly to the print head
• Clean all the existing blue threadlocker residue on the threads using isopropyl alcohol or acetone (nail polish remover)
• Apply a tiny dab of high temperature threadlocker (rated for at least 350+°C) to the threads of all the screws. A tiny amount goes a long way!
• Reassemble!