Any advice on an attorney/organization to talk to in order to get a letter from an attorney to get the landlord being reasonable or similar instead of turning this into an expensive legal battle?

I had actually sent a letter and tried to call the owner several times on this.

I wanted to try something different because I receive a lot of similar letters and postcards for all my properties, that doesnt catch my eye much.For the cold calling, we use mojo dialer which has a built in crm and the power dialer.

Sometimes a letter to the seller can turn the tide in your favor.  

He is also willing to furnish a letter from his US brokerage firm to prove he has ample funds to cover for rent and expenses.What would you do?

The attorney may spot issues and recommend an objection letter.

If you are buying as a primary be prepared to write an "LOE" Letter of explanation on why your moving out of an SFH into a MF 2-4 unit.

We sent one of those “love letters” through our agent and he sold to us for the same price as the other guys offer because he liked us.

I'm assuming they did, but make sure that they followed their bylaws to the letter in making that change.

Buyers should have a strong investor focused lender and updated pre-qualification letter dated within 90 days and a team on the ground that can facilitate short term (sometimes virtual) showings and responsive/creative dealmaking ability.