There is a 1500 sqft house that is needing remediation work done.

3) My thoughts these past few days have been that an annual PM inspection in Jan 2016, 2017 and 2018 could have remedied the issues above and the response from the PM is pretty weak. 

A landlord would have no enforcement power as the only remedy for a landlord is eviction.

I am a real estate agent in California, so some of the sale costs would be remediated.

No, you don't have to allow a remedy.

You are required by both state and federal law to remediate any lead-containing products (paint, putty, etc) and obtain a de-leading certificate.If you have a handicapped tenant or applicant, you may not refuse to rent a unit to him or her.

We had to pay a remediation company to clean out the pesticide.

It does not say what the remedy is if they are lying.

Unless they formally agreed to make the repairs you're asking, the only other way you had a firm contract was to accept it 100% as is and proceed based on the original contract - sans request to remedy addendum.If they never agreed to your repair list, they are fully within their right to back out.  

@Chad Forgue Re: Subdividing, not having funds is something that is remedied by a partner in this situation.