As soon as something is well-known, it will be abused by spammers/scammers.
Could you elaborate on why you put your public key in well-known and also how (and for what purposes) you use your air-gapped private key? As an average user, I’ve always been worried about private keys being stolen or lost.
Not all my private keys are air-gapped, but the encryption key is, since I don't need to decrypt my backups, and don't expect to receive encrypted email very often, so why take the risk? I have an old laptop which is not connected to any network and that I only use for this now: I plug the USB key with the private key, decrypt / sign whatever I need to and that's all. It takes me a lot of time, but I don't do that more than a few times every year.