I agree with point 9, it seems very silly of kingston to wake up columbo with the su****ious paintings in hand, rather than hide them, he had all the time.

As for columbo, we know how clumsy he is but also how he's willing to do anything to solve a case, even leasing an apartment, so I would say he fell asleep by accident, but then he tried to make use of the accident to solve the case, for example checking kingston's bag with the paintings, and he'd have caught him red handed!

Also agree, it's very strange for the police to call columbo at kingston's number overnight, as in assuming he's innocent and he doesn't spend the night out murdering people, they would presumably risk waking him up.