Congratulations on your cute kitten! He's going to be a lot of fun and joy for your family
Microchips are useful in more ways than identifying carcasses. We just had a recent news story of a cat that wandered into a news reporter's yard. When trapped, his microchip lead directly to the cat's owner so it could be reunited.
We in Rescue hear of many cases where microchips have helped. It's not foolproof, it's not GPS enabled, but it is a simple way to make sure if someone wants to find the owner of the cat they can
Definitely work on preventing the door darting. He should never be allowed to walk or run through the door. As mentioned, if leash walking carry them...or I know some that teach their cat to go into a crate that they then take outside... this has the added bonus of giving the cat a good association with crates... making it easier to crate for other reasons.