What's a good action for my Tbird? I had it high and low but I get horrible tone on any frets 9 and higher
Good action is highly personal and subjective. It's essentially defined as what works best for you. I have my Epiphone Thunderbird Classic set at 2.25 mm (E string) and 1.75 mm (G string) bottom of string to top of fret - BUT - I use smaller gauge strings than you, so you will probably want something higher.
Also sounds like you may not have your truss rod adjusted to give the correct neck bow. So that would be the first thing to check and correct.
To adjust your truss rod, you need a capo, a 0.015 inch feeler guage, and the appropriate wrench or screw driver to fit your truss rod.
Also, you can break the truss rod and/or ruin your neck if you do this badly. You are warned.
Once you've got the neck adjusted correctly, try setting your low pitch string (B in your case, I think) 1/8 inch above the top of your 12th fret by adjusting your bridge height. (You can't adjust individual saddle height on the three post Gibson/Epiphone bridge.) You will mostly be adjusting the rear-most screw on the low string side, but you might also do a little adjusting of the front middle screw.
Then the same sort of thing on the high pitch string side (D for you, I think). You want to aim for just under 1/8 inch - a tiny bit lower than the B string.
Once you've got that, go through each string along the entire fretboard checking for fret buzz. If you've got fret buzz, your truss rod isn't adjusted to give the correct bow, or your frets or neck is fucked up. If the neck is bowed correctly and not messed up, you will have to raise the action to lift the strings higher to escape the fret buzz.
If you don't have buzz, raise or lower the action to your liking. Commonly, low action is sought after. Too low and you will get fret buzz, then you have raise them back up a bit until no buzz.
Have fun. Don't break your truss rod.