What's wrong with my setup?

you can use a dimmer but you will have to change the settings on it regularly if the room has temp fluctuations..

I had a dimmer in my room for a long time and I had to change settings on it 3 times a day because of fluctuations...

If I were you I would get a uth and a dimmer for right now and save up $79.99 for a ranco or johnson thermostat... You can get them at www.reptilebasics.com

A dimmer will be much better than nothing at all.

Also if you get a uth and dimmer you will also need a digital thermometer with a probe so you can measure the substrate temp above the uth...

i would add another hide also might be to hot or cold in the one
hes probably lookin fer a space to get comfortable