You have three different tax returns that need to be filed. You have the final 1040 for your father. You have the 1041 for the estate, and you have the 1041 for the trust. As personal representative, you certainly are the only person in position to file for the estate. You would probably also be the authorized party to file your father's final return. The trust return would be the responsibility of the trustee. I do not see any harm in your reviewing the form ahead of time, but the trustee would not be obligated to provide it to you ahead of time.
Given the situation with your brother, you definitely need to hire a lawyer to assist you.
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I agree with Attorney Frederick's answer on the number of tax returns and who is responsible for filing them. Your MD attorney can send everyone a letter of explanation.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.