Probably not. If person in possession has inheritance interest, he is entitled to remain in property. Review with your attorney.

Possibly. I need more facts and revire of order to opine.

Each of your rights depend on specific language in order. If no agreement can be reached, RFO may be necessary. Review the order with your attorney.

Your attorney may request replacement check on your behalf.

Your attorney may complete Small Estate Affidavit which will authorize you to sell vehicles and obtain access. link...

You need assistance from estate planning and administration counsel. Book a consultation.

You may petition court to appoint father guardian. Enforcement in Mexico governed by Mexican Law.

You are describing pre-death trust contest. Too complex and too many questions to address in this forum. I need more facts, copy of estate plan...

Yes. Link explains: https://www.courts.oregon.gov/courts/lincoln/help/Pages/probate.aspx

Only probate court has authority to appoint executor. Not brother. You may file creditors claim in probate matter.