Mr P,
first of all you did a serious mistake leaving F1 and decided to work under TPS with EAD. Maintaining F1 supposed to be you main concern than TPS, you could have atleast consult with International advisor to take minimum credit course in college or university and use TPS EAD. In that situation, you could have easily remain in F1 if TPS expires after Dec.
Now Applying for Cos (Change of Status) to F1 is the same process of getting I-20 from college, SEVIS and apply to USCIS and wait for their decision. Hope you get F1 soon before class starts but who knows, it might be delayed or under worst condition, it might be denied as you already changed status from F1 to TPS. You could have spoke with lawyer before leaving F1,I think that's a blunder mistake you did. If TPS didnot extend and F1 did not approve, what choice do you have left my dear.