This will need to be remediated by a foundation company.

In regards to the mold, you may want to have a remediation contractor take a look and quote a proper repair that you can negotiate with the seller on.

Worst case - you learn something about water/crawlspace remediation and spend some time, you can always get your earnest money back and get out of the contract if the numbers don't add up.

Alert them also that you will begin remediation activities within x days of closing and will not be responsible for providing alternative accommodations during the remediation as this will help inform their decision to move.

I am the only one in the community that has made this complaint to the builder.HVAC techs have come out multiple times to try to remedy the issue by adding vibration pads, padding wiring, changing the air filter and they will be coming again in a couple weeks to install a hard start.

People tend to question less when it's all standardOne other thing, limit the sellers remedy to retention of the earnest money.

Either way, the exact issue and remedy should be communicated to you clearly.

Prevention of problems is far less costly than remediation.

There has been an environmental remediation company sent in to work on the spill (let’s just say it was almost 100 gallons, in order to keep this anonymous). 

Still I recommend letting professionals determine the best remediation.