Android - Remove credit card from google wallet, will it affect purchased apps?

Of course not. The only way the would be affected is if they were still pending purchases. I have removed a card previously and all my apps were still intact.

Your purchases are linked to your account, not to your cards.
However common sense still applies. If you have in-app subscriptions set up on the card that you've removed, than the next charge will fail.

Yes.

Your in-app subscriptions attached with that card will be disturbed. And, an app developer would be unable to refund money if you've purchased that app using that card (but, this is solved by contacting Google support).

But, you'll not lose any purchased apps. Even pending purchases will not be affected if you attach a new card with the account. Otherwise, it'd be cancelled.