This is a truly unfortunate situation for your brother. As others have suggested, you need to speak with an attorney soon about the situation. I suggest you find one attorney to investigate the facts surrounding your brother's personal injury and whether there is a legitimate claim. Second, a different attorney (generally, most attorneys do not cross-over between these two areas of law) to investigate whether a guardianship (I'm assuming he is an adult) may be needed for your brother.
Generally, these questions are very fact intensive. The most important questions is whether someone would take the time to legally pursue you due to the lack of insurance. I highly suggest speaking with an attorney about your particular situation.
You'll want to speak with an attorney that is willing to due some investigation into the matter as one defense to the matter would be, "how do we know you didn't put the rat in there and take a picture?"
In my experience, the contaminated food claim is far more difficult to prove than one would initially believe.
If there truly is no property and only debt, generally, opening a probate does not make sense unless there is some pressing reason to do so. The rules on probate can vary wildly from state to state. I suggest you find an probate attorney in your area to assist you.
Whether you decide to probate the Will is dependent upon whether the cost is worth the benefit. If you can' talk someone into releasing the check to you and it is a substantial amount of money, it would make sense to at least...
Retain an attorney to fully represent you in your case. Many Pro Se litigants fall into the belief that they can retain an attorney to "advise" them on what to do, then the Pro Se litigant can "save money" by doing it themselves. Some may disagree, but I am of the mind that the attorney is either "in or out" on your representation. If an attorney is willing to agree to such fractured representation, they are likely "out."