Lots less work and if you are lending commercially only, less liability.

So a loan may be made without recourse or, often with limited recourse or with "carve outs" with or without liability under certain conditions.Public service or benefit loans can take on various projects and may meet the Community Reinvestment Act requirements, there are then added benefits or incentives for banks to make these loans and to do so on a non-recourse basis. :)

If we had them sign some sort of release of liability, would that ensure we would be done with this for good?

The reason is for liability when there isn't an emergency. 

When an investor says they CARE more about a house than a PM, that is actually a LIABILITY, not an ASSET. 

The car payed off is getting rid of a liability.

Without anything meaningful to contribute (that you've mentioned anyway) then you're a liability that a developer isn't likely to pay for.

I noticed there is no Assignability Clause (Buyer may assign and thereby be released from any further liability under this contract).

Legally he probably had ZERO liability, and so did his insurance company.

For liability protection - do not be negligent and you should be fine.