In my leases I clearly write and explain to tenants that we will remediate any issues uncovered in the 1st 30 days at our own expense.

You need to decide if you seriously want to pursue a remedy.

Once you know, you'll be in a better position to respond.BTW, while suing for specific performance is a real remedy, it's going to be expensive and slow. 

I also requested additional documents like estoppel certificate, mold remediation that the seller isn’t able to produce.

Seems like the quickest and easiest remedy to this situation..

I would ask them for a remedy to the "too much" situation... might be fun to pick their brain. 

Termination of periodic tenancy).I'm not quite certain what the landlord's remedies are if you don't provide such notice.

Now my buyer Is thinking about backing out and I'm wondering what kind of legal remedy can I seek if this happens?

In any action with respect to this Lease, the Parties are free to pursue any legal remedies at law or in equity and the prevailing Party in litigation shall be entitled to collect reasonable attorney fees and costs from the non-prevailing Party as ordered by a court of competent jurisdiction"I think this should protect me.

Lead paint itself is not dangerous - it's the lead paint that is deteriorating—peeling, chipping, chalking, cracking, etc, that is problematic and requiring remedy.