Sorry to hear about your difficulties. Couple of quick things.....
1. Licensing - I am licensed in CA and don't know Maryland BUT - the state consumer affairs office takes complaints against licenses VERY seriously and that is an option for you. Laying out a string case with documentation and it kinda sounding like since you are knew to the game;;;:: he may be purposefully trying to "work you" because of your inexperience.
Also re licensing - here there are strict guidelines contractors must follow concerning acceptance of payment prior to the rendering of services. Contractors will many times accept or take "draws" against the project for work that has not been compelled performed. Again, I don't know Maryland.....
2. Surety Bond - in CA ALL contractors must have such a bond and you can file a claim against his bond.
*** Doing either of the above in CA would get the contractors attention quickly. As the consumer; you are protected and the contractor state licensing board is hard on contractors when they try and mistreat consumers. Again, this is CA and I don't know Maryland...???
3. Come to Jesus Talk - I don't know the conversations you have had with him/her, but it's time to be very clear and forceful about their lack of performance and possible poor estimating and diligence in performing per contract details (don't know what they are, but you get the drift! ---- MESSING WITH MY MONEY IS LIKE MESSING WITH MY EMOTIONS!!)
4. Attorney - check and see what the would cost for an attorney to write a letter on your behalf re your intent to sue re breach of contract and yada yada yada,,, misleading professional quotes,,, and whatever else they can put together.
From state to state things vary,,,,, I am primarily investing in Texas right now and other than a few trades, ANYBODY can be a contractor or perform various types of construction work. This was complete culture shock to me! Here, if it's not Plumbing, electrical or HVAC, anybody can do whatever. These trades must be licensed. Any other trades you haves problem with you simply have to sue in court.
If I were you, I would do so research and get schooled up on the ins and outs of contractor licensing in your state and use the responsible agencies to help you if possible.
Lastly- trying to to be too lengthy, you can fire him (in writing) citing cause for such action and hire another contractor to finish the job since you are essentially losing money everyday. --- then sue him for whatever he has been paid fur and not finished.
Hope some of this helps!