The law will not compensate you merely for the fact that you were involved in an accident. Instead, you must be able to prove that the operator of the vehicle was negligent in causing the accident and your injuries. Without more information (such as a police report), it is difficult to tell from your description whether a claim can be made. You should contact an experienced personal injury attorney to further discuss a potential claim.
Besides doing research on your own regarding Maryland attorneys who can handle your case, you can also contact some Maryland bar associations who may have lawyer referral services that will connect you with a personal injury lawyer.
Unless there are some factors indicating that the movie theater was negligent in some way (lighting, failure of steps to meet Building Code, etc.) and that the movie theater's negligence caused or contributed to your fall and injuries, you most likely would not be able to bring a case against the theater.
From the description provided, it is unclear whether you would have a legal malpractice claim, but you should immediately contact an attorney who has experience handling legal malpractice claims to discuss the particulars and finer details.
What you have heard is correct - you can't sue for a specific dollar amount. Each case, however, has its own individual value and you cannot rely on other cases as bench marks for yours. There are various types of evidence that an attorney can put in front of the jury in an attempt to quantify a client's injury, but you are still at the mercy of the jury.
You certainly have the right to change lawyers if you do not believe you are getting the attention of your current lawyer. The fact that you do have an attorney should not be a detriment at this point in the case.