This is one of my least favorite things to see in Probate practice. We know that the will represents what the decedent wanted, but some boilerplate in an bank account agreement contradicts it. Unfortunately, as a general rule, a JTWROS agreement trumps the will. For the will's directives to control, the JTWROS would have to be set aside on grounds that your father lacked capacity at the time he signed the account agreement or was subject to undue influence. This is a trap in the law that...
The trust may very well be an attempt to circumvent your community property rights. You need to consult an attorney to review the trust and possibly challenge the transfer of the homestead and possibly other assets into the trust.
I would guess the intend of the waiver is only as to wrongful death benefits, which can be received by heirs or the estate or both. However, "as well as the Estate" is ambiguous in this context, and you should request a revision, or interlineate a change, before signing. Insert the words "any wrongful death proceeds received by" so that the sentence reads .. . "as well as any wrongful death proceeds received by the Estate of mother . . ." Also, add a sentence: "This release in no manner...
You will need to retitle, but the executor will need to deliver you the titles signed by the executor and a copy of the letters testamentary to do this. You will not be able to get your annual registration without updating the title.
Since there is no will, muniment of title is not an option. You are correct that some probate is necessary. A power of attorney is no longer effective. Full heirship would be expensive (about $3500), so research a small estate affidavit. Using an attorney, that should cost less than $1000.
If you friend has a guardian, he has been declared incapacitated and has no ability to sign a power of attorney. In any event, to change a guardianship, you must file an appropriate application with the Court which created the guardianship to change or terminate the guardianship. If your friend wants you to be his guardian, the Court will consider his desire in making its decision.
If the will created a trust for your children, and it should, then the beneficiary should be 1) primary = spouse and 2) secondary = Trustee of Testamentary Trust per last will and testament. If you have ANY doubt what you are doing, consult the attorney who drafted the will. If an attorney didn't draft the will, hire one and be prepared to shred what you have.