Sorry to hear that. How old was he?
Don’t declaw the new cat unless you absolutely have too. I have found that cats love to sharpen their claws on closed cell foam.
My black as Satan cat used to open closed doors too. I would come home from work and and find all the cupboard doors open that he could get too.
Mine, too, but it was bathroom doors. Couldn't stand for anyone to close a bathroom door. I'd warn visitors to lock the door but they never believed me until it was too late.
Hugs to lil' Bill and poor kitty.
Better than drinking anti-freeze.
That would be painful.