I've also assumed VA loans where little cash was used (seller had low/no equity).

I believe the investor may need a commercial loan at that point or could do 3 separate loans since they are on different parcels.

If you are getting a loan no there is no way to protect yourself from crushing your credit or having a foreclosure against you if you are the borrower. 

We have secured a home equity loan against our home (which we own out right with no mortgage payment).

Did you try a local CU or bank for a construction to permanent loan?

Are there any loans out there that require less than 10% down?

So a loss of about 55k We did a lease to own option so I could immediately take over expenses but keep their primary resident loan and interest rate.We agreed to a deal which would cover all their expenses at closing, their remaining loan balance, and $45,000.

Explore FHA loans and mentorship opportunities from experienced investors.

I think you would be wise to sell and use the VA loan for your new home. 

Mortgages are the last thing to default for a homeowner and appreciation has been so high in Canada that every homeowner who has purchased before 2022 has gained equity and could just refinance their loan over a longer amortization before defaulting.