Disassembly of this little piece is tricky ... the thread comes loose but the nozzle is still stuck on the filament tube.
Carefully put the heat block in a vise (vice) and pull heavily on the nozzle while rotating it with a wrench. It will come off.
If you managed to damage the hexagon inside the headless screws that fix heater, sensor etc. - try a hot air gun.
The aluminium block does expand more than the steel screws. Good luck.
Last resort: Carefully drill out the screw core, then remove residues of screw, before inserting new ones. Takes patience.
Pushing the steel tube out of the block is again tricky: It may need a soft blow from behind (hammer and wooden pad).
I'm in the process of renewing the PTFE tube inside the steel tube... that whole ensemble is available from the Kodama store, as well as the complete hot end (in case you don't want to rework the old one).