Is there a way to reserve online & nit have a added booking fee ?

Get Movie Pass. You can see one movie per day for 10 bucks a month. It cost nothing extra to book through their app

Sometimes it doesn't show up, but I don't know if it's a glitch or not.

No. The other option is buying tickets directly from the theater . They do not charge a convenience fee.

Idts

There seems to always be an additional fee, but it is great to be able to not have to worry about what seats you are getting.

Yes I think so but I haven't tried yet