When they replaced the timing belt, did they also change the valve cover gasket? The misfire code and consumption can both be due to a bad valve cover gasket letting oil into the combustion chamber (this can also throw an O2 sensor code depending on how bad it is.) Otherwise, its the valve stem seals and/or piston rings.
I feel your pain when it comes to car repairs because the timing belt in my MSP snapped on me two weeks ago and I was in a similar predicament since it was my only car. I had Pepboys quote me $2k for a timing belt job and replacing valves and decking the head because they claimed my car had an interference engine and that I more than likely bent some of the valves. After I called bulls***, and speaking to a Mazda tech, who confirmed it was non-interference, they dropped the price but still wanted over $1k. I ended up doing the work myself and replaced the timing belt, water pump, all idler pulleys and valve cover gasket, all for a paltry $250! Best part, she purrs like a kitten now, no issues, no bent valves.
What they charged you for the work is insane and you need to pursue this. For one, they didn't fix your oil consumption issue plus they seriously overcharged you. This is the problem with the autorepair industry, particularly franchises. If you were a car-illiterate or novice, you can easily get swindled into paying for unnecessary or incorrect repairs. In my case, if I had been a novice and just ok'd every repair suggested by the Pepboys guy, I would've spent over 10 times what I actually spent fixing it myself. In the future, I highly recommend doing some reading on your car and engine and start doing some repairs yourself so in the very least you will have the confidence to call a mechanic out on his bulls*** rather then just ok'ing everything out of panic.
Btw, it may help if you posted a video of your car idling when cold and when at operating temp. Just do a walk around and include a shot of the tail pipe when the engine is cold and when at operating temp. It can be really difficult to diagnose a car without any kind of testing or measurement, particularly over the internet, since similar problems can have different causes.