There is no requirement that anyone be notified as to the death at the time of death.
As to notice of filing of the will, if you had been estranged from your father for so long, how would anyone connected with him at the time of his death know anything other than old addresses. Notice to "last known" address is usually proper notice. Moreover, in probate, if addresses are unknown, notice is given by publication in a newspaper. If the publication was in a California newspaper you would have been unlikely to see it in Texas.
As to the validity of the will, do you have a full and complete copy of the will?
As to the signature, signatures do change over time. If you are unable or unwilling to retain an experienced probate attorney then you should go to the courthouse yourself and ask to see the file yourself, look at the will, look at the orders, copy the will, check it against the California statute on wills, check compliance with the court orders of notice and go from there. If you are lucky there will be an "attorney of the day" on duty who you can ask to take a look at it. The clerks will get you the file and allow you to look at it but clerks are not allowed to give legal advice. You would have to make copies at your own expense and go from there.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.