You most certainly do live in Pennsylvania. Similar things have happened or almost happened to me while I lived there.
The short answer to your question is, as noted by the other attorneys, yes, you may sue, and you should get a recovery. Get a good lawyer who has experience handling auto claims; he or she should be able to help.
I would strongly suggest that you obtain legal counsel to advise you on this. In addition, I suggest that you be very careful in discussing the matter on a website such as this, there are too many ways what you have written can be misconstrued.
You DO NOT have to pay. When you discover a mistake in your medical records, under HIPAA you are permitted to send a "request to amend the record" and they must respond and give you reasons if they will not amend.
I suggest that you adress you request to the Health Information Manager or Medical Records department and not the physician. They may have a speacial form that you have to fill out, but it is relatively straight forward.
Most hospitals have a charity care policy. It will require you to provide your income and personal expenses, but it will also permit them to reduce your bill. You could also negotiate to the medicare rate, although many insurers now pay below medicare. The main thing is, you can negotiate the bill, don't let them tell you they don't.
If you find it difficult to negotiate, you could hire an attorney to do so for you.
In addition to the very good comments of the other attorneys, you should be aware that you might be considered to be practicing tele-medicine in those states in which the individuals live to whom you are giving this advice. You could run into significant licensure issues in that some of these states, which in turn could jeopardize your license in the state in which you practice.
In other words, 'Here be Dragons.'
Unfortunately, hindsight is 20-20. Had you had a Durable power of attorney in place, granting you this authority, this situation would not have occrred. As of now, there is probably little you can do in this situation, unless you can establish that your friend is competent and being 'held against his will.' Considering the circumstances, I believe the chances of establishing this are relatively small.
All this being said, you might want to see a local attorney and explain the situation,...
Yes, you can be sued. You have a dog that you know (or should have known to be dangerous, you did not properly constrain it (a reasonable person would have knownit might go through the screen door) and (as a result) it bit someone. As the other attorneys have noted, your homeowners should pick it up. However, if you do not have insurance, you should contact and attorney to defend you.
It is of course possible to sue, but there are a few issues that need to get clarified.
For example, how would you prove this without some evidence? If he ate it, it is gone. Further, who are you going to go after, McDonalds? Finally, how do you know hwatever is making him sick came from the sandiwich?