You could potentially make an allusion to “the answer to life, the universe, everything” and follow it up by saying something about how we may never know the answer (though you suspect it’s 42), but he lived his life as close to that true meaning as anyone could.

I’m sorry for your loss, but I’m happy to hear that you have some really precious memories you’ve shared together. Grief is funny in how it touches the things we love even when it’s not funny in how it touches the people we love.