I haven't had the problems you have, but I do have a bit of a problem in the fact of overwolf is required to be running in order to use the FTB app. I can understand it being required to be installed (due to the partnership with them), but required to be running? It feels a bit....heavy-handed to have that forced apon us, that along with ads being shoved in our face while the game launches. Now, I understand the need of ads to help support FTB and their efforts, but that doesn't mean I have to like it
Sorry for the rant there. What you could do (and what I am considering doing myself), is you could use a 3rd party launcher, like MultiMC, and just copy the files from the FTB install directory into MultiMC, and then you can close out of overwolf/FTB app/etc and only open those up when you want to check for pack updates.