As suggested I’d try acetone and instead of a torx bit a good screwdriver. I know it seems like the same as a bit but it’s not. Even if you had to get a small set or single from a snap on truck it would help.
One additional thought. Try applying your heat as you did previously then apply your Kroil. As the screw/threads naturally cool, the Kroil will be drawn down into the junction. It has worked for me on larger parts.
Choose wisely...blue Locktite is YOUR friend, red Locktite is the friend of the assembly!
I'd try this and then follow it up by putting the gun in a padded vise, put the torx bit in a holder and lock onto the bit holder with a set of vice grip pliers.
Apply a moderate amount of torque to the screw with the vice grips & torx bit assembly, and then tap the end of the bit holder with a small hammer. Basically using it like an impact-driver.
I've "jarred" more than one stuck screw loose with this type of technique.
Used in large amounts on properly prepped material, blue loc-tite can be really, really close to red.
BTW, color isn't necessarily a true indicator of properties. The loc-tite product number is.