Your questions pose many issues that would be better answered by an estate planning attorney. That being said, amendments to trusts must conform with the requirements for amendments, which are dictated by the original trust document. Look at the original trust document and see if the amendments conform with the requirements.
Unfortunately for you, the circumstances you describe leave you very vulnerable to challenges to your actions. That does not mean that you did anything wrong or that you weren't entitled to do exactly as you did. But any business that needs to rely on your documents in order to act will proceed with caution. I suspect the trustee that was replaced by the stroke of your pen is also suspicious and considering a challenge to your authority. The fact that no attorney was used does not mean the documents are not legal, but it adds to the whole picture. Other facts will certainly be relevant, including what your relationship was with your father (were you taking care of him), what was your father's mental condition when he signed the POA, and what are the specific terms of the trust (who are the beneficiaries, etc.)?
You really need to bring all of your papers to an attorney for review. Feel free to contact me, an initial consultation will not cost you anything. Regardless, good luck.
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