Its not clear from your question if your mother is still alive or not. As my Estates and Trusts professor loved to say, "A living man has no heirs". What he meant was, heirs are determined once someone has died. Until then, they have a legal right (with very few restrictions) to designate any beneficiaries they want. The determination of whether or not you are your mother's heir is academic without knowing the context of why you are trying to determine this.
This sounds just awful. Although it may be difficult for you to pursue a case against the caregiver, it is probably worth contacting a local attorney for some guidance. Gather up everything you have, organize it chronologically and take it to a lawyer for review.
You should consult with a local Personal Injury Attorney right away. The Statue of Limitations on your action is running and soon you will not have the option to file a complaint. Most PI Attorneys will not charge you for an initial consultation.
First you should contact him in writing and make sure that you provide him with your new address. This will set in motion a thirty (30) day window for him to return the security deposit. If he fails to do so, you can file suit (i.e. sue him) for two (2) times the actual deposit. Such a law suit can be started by filing a Complaint with your local District Magistrate. The process is relatively straight forward and you are not required to hire an attorney to do this.
As with most Landlord/Tenant matters, the answer to your question can be found in your lease. A careful review of your lease will most likely answer your question. If the lease is silent on this matter, then (with proper notice) your landlord may increase your rent for a subsequent Lease Term. There is no limit to how much this can be increased.
This entire answer is based on the assumption that your unit is NOT section 8 housing.
This sounds like a case of a landlord helping him/herself to personal property in an attempt to offset some alleged damage. This is considered "self-help" and that is an action that is not permitted in Pennsylvania. At a minimum, the owner of the property should file a complaint with the local Magisterial District Judge (so long as the damages are for $8,000 or less). At the maximum, this may be a criminal matter and the police should be called.
Read your lease very carefully. If the lease does not give you clear guidance on how to proceed, you should contact a local Landlord Tenant Lawyer to help guide you through the eviction process. Under NO circumstances should you exercise "Self Help" (ex. changing the locks, disconnecting utilities, etc.).
Your landlord may not have a legal obligation to provide you with a copy of the lease, however her statement that "legally she can't give you a copy" is just plain wrong. There is NO law stating that a landlord is prohibited from giving a copy of the lease to the tenant.