That is a correct usage and it's a pretty common term. It can also be used as just "even more" most of the time, but the difference is only in preference. Last sentence would be better as: "I hope you got a gist of what I was trying to convey with the sentence." (okay for informal) "I hope you understood a gist of what I was trying to convey with the sentence." (better for formal)

Aloha Harry! :-) Yes, "even more so" is a pretty common phrase & you used it correctly in your example. I can't think of any other way to say that except for "It's very difficult to operate, and it's even harder to correct its problems." Other things since I'm here - You said: "how often do you use "even more so " or there`s some more popular substitute" how often do you use "even more so " or IS THERE A more popular substitute? "Was it correct to write: It's very difficult ..." IS it correct to write... "I hope you got a gist I try to convey within the sentence." I hope you got THE gist OF WHAT I'M TRYING to convey within the sentence I've never heard "gists" being referred to with indefinite articles like "a". But that could be another fun dialectal difference. I also need to have the whole phrase: the gist of what A hui hou, Pat