Surely you can supply more info. The name of the camp, their previous DTV experience and success rate, the length of your course, how long your funds seasoned, were there any additional documents requested, etc etc.
He may have gotten a new passport last time but it doesn't mean that your old passport was expired. Your recent experience is the correct way, extension stamp till the expiry of your passport.
TM30s don't have a real validity date, there is a proposed length of stay at the accomodation when filed and that might be the date that you see. Every valid tm30 is invalidated by your next filed TM30
Write a letter on company letterhead stating you are a current employee and authorizing yourself to work remotely in Thailand. Also note that you'll not be interacting with Thai businesses or individuals.