Here's the deal: You don't need to withdraw and return the current security deposit just to collect the additional $100.

Yes, you can deduct the 8 days rent from the security deposit.

In fact I had one done that size over the summer from some real slobs who moved out, and it required an inordinate amount of deep cleaning including almost one full day just on the filth of the kitchen floors, and it was $400. 

Now, over a year and a half later, he sent a certified letter last week demanding the security deposit or legal action within 30 days.Please advise. 

If it's not a holiday, I would say, "No, the deposit remains in place until your lease ends."

Quote from @Phillip Austin: There are two alternatives to a security deposit, which I speak about in my book.

This has been my experience: "As to the remedy plaintiffs seek, the case law reveals that "the equitable remedy of specific performance is routinely awarded in contract actions involving real property, on the premise that each parcel of real property is unique" (EMF Gen.

After searching more, I found a few BP post where people seemed to have one account for all deposits, and keep only deposits in there.

Consider all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

@Sean O'Keefe can I get a copy of the real estate professional logbook?