If you can’t get a chuck off and no one else can help and if you can find him maybe you could hire Doctor Lefthandthread.
This DCD796 had la busted chuck with the bit stuck in it the only options were a dremel 3000 and a Metabo angle grinder. I had to quite brutally saw it off without damaging the threads of the drill too badly.
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Idk if u tried it but if theres a bit stuck in the chuck grab a hammer and beat the hell out of it. Usually itll force the chuck open enough to expose the torx 20 chuck screw.