In the quest secret to the cellar, I didn't know that you had to find the key the following evening and now it keeps saying nothing is in the hole is there any way to progress on that?
You actually can't find it the next day according to the walkthrough, you have to wait a day. (I don't remember that being a thing.)
Just try different nights while Thomas is working, you'll eventually find it. You will be fine, I have put off getting the key after getting the quest for weeks sometimes, especially back when following him down there was the end of content for the cult quest.
The walkthrough actually says it a little funny, Tuesday at 0-5:00 actually starts after Monday night. So after his work on Monday, Wednesday or Saturday nights, is when he goes down into the cellar. So he is carrying it on those nights.
So look for the key in his room hole during his work on Tues, Thurs, Fri, or Sunday nights. Make the copy the next day and replace it that evening. (I have never tested it out, but I do wonder if anything happens if you don't put the key back.)
Then when the clock strikes midnight on a M,W, or Sat night be ready to go down there.
(I think I got the days of the week right, but I might be completely wrong, just keep trying subsequent days and you will get it.)