The next week, I see that somebody had, in fact, deposited the check that I originally sent over a month ago, the first day possible after I made the transfer via PayPal.

Because the title was transferred with a Quit Claim Deed. 

This may or may not pass muster in our case.Which, jumping to conclusion, implies that there is no standard way of "transferring" the loan directly, in order, having the 3 of us (me, buyer, bank) sitting at the same closing table and performing 1 atomic transaction.

Should I just let it go, sue the seller for non-performance or transfer my contract to a more patient investor?

Through that family member's life they have had some knowledge skills, and abilities, to accumulate a net worth which allows them to participate in this investment, and those may transfer, albeit tangentially, to REI. 

Most people have the app nowadays and it's extremely convenient to transfer the funds into your bank account. 

If the bank were to find out at a later point in time that one of the people was no longer on title or that ownership was transferred to an LLC they would be able to call the full note due.

Yes, technically the escrow is for taxes and insurance, but in reality it's a checking account.In the event that you refi your mortgage, that escrow balance comes back to you because it is essentially your money held at the mortgage holder's office.When I'm doing accounting, I transfer the escrow portion into a separate "checking" account. 

I also would suggest an online payment, I like using Cozy also, very easy to set up, but it does take a bit of time to transfer. 

In some cases transferring an asset to another name or entity may amount to a fraudulent transfer, exposing the person to additional liability.