A: My condolences for the loss of your mother. You most likely do have recourse, but you should seek the assistance of a trust and estates litigator as soon as possible. Even if the quitclaim was valid, which likely it was not, that deed would have applied only to the home and not the contents or anything else. As well, the power of attorney ended when your mother died.
Believe it or not, and sadly, notaries in California have no legal duty to make an assessment of a signer's mental capacity.
A: If your grandmother's home is still in her name, and I'm assuming she is deceased, you must file for probate. It is the only way title to the property can pass to her heirs, typically children, then grandchildren. It's not clear when you say there's a lien on your property. If you are referring to your grandmother's property, that's not likely or can be challenged. Your father also would/should not have been able to use your grandmother's home for collateral on a loan without first at least starting a probate of your grandmother's estate.
This is not a probate you would want to try to handle without the assistance of an experienced probate attorney.
A: You need to have an attorney look at both the trust document and the petition your brother filed. You seem to raise valid objections to your brother's appointment as successor trustee. If you were properly served with your brother's petition, you would have had to file an objection to that petition. If you were not properly served, the court's order can be challenged.