The listing agreement should have a clause allowing you to let him go with notice.You should be getting communication from him at least once a week, or whatever he promised in the listing presentation, good bad or indifferent.

Can time spent researching/analyzing investment opportunities, traveling to see opportunities and education  be considered as part of the time spent minimums? 

@Jacob Calbillo there is no minimum amount of homes - the definition of a park is multiple mobile or manufactured homes on one piece of land that is usually owned by someone else.

We came close to getting him to sign a purchase agreement a few times, but each time he ended up backing out because he just wasn't emotionally ready to sell.

Experience (maybe 5 years minimum). 

Are you signing all documents, contracts and agreements with your corporate title?

Those two alone are a minimum of 60 days (I would think).

A lot of questions here...As your dad has a 50% interest, and a trust owns the other 50% of which you and your two siblings are the sole beneficiaries (I presume), it might be advisable to, after the trust interest is distributed, to have your father, you, and your siblings contribute your interests to an LLC in exchange for shares of the LLC (usually called "units").The property would be re-titled in the name of the LLC and the LLC can use it as collateral for a loan.It's usually highly advisable to engage an attorney to draft an operating agreement in this scenario to get everyone on the same page about ownership interest, who is/are the managing member(s), what happens when someone wants to sell -- do the existing members get 'right of first refusal', what happens if a member passes away, etc.

This rent to own agreement has gone terribly wrong.

However, mine isn't and requires a good bit of principal pay down included with the minimum monthly payment.