If they are uncomfortable and concerned then I would evict.

I have found one team in Florida that I pay a small margin more for the equipment and install but that are very detailed orientated, professional, stand behind the products and perform a follow up system check weeks after install.The second most important thing seems to be the routine maintenance for us in the Southern states. 

You may just have to enforce him staying and deal with the uncomfortable time from now until his lease is up and he can leave then. 

I always send owners most, if not all, of the pics I take at their properties, and I always write up my repair recommendations for them directly from the photos.The key to taking useful pics is to have an organized system of HOW you will routinely walk through a property.

Apparently Roommate B has been cornering Roommate A in the common spaces and standing uncomfortably close.

However, you're not a bank or a corporation so if you are uncomfortable handling and managing debt take that into consideration.

I heard first month's rent of any new tenant plus 10% monthly for all routine issues managing the property. 

To piggyback off @Patricia Steiner's helpful response, please note that the specific PHA that the voucher is approved through evaluates what is "reasonable rent" based on the HUD values, but in our jurisdiction it uses them as a MAXIMUM, and reasonable rents are often below that HUD FMV.For example, in Cleveland, CMHA lists that HUD's FMV on a 3 bedroom property is $1200, and their adjusted maximum for the zip code is $1320, but we routinely get 3 bedroom vouchers and the rent determination comes in around $850 based on the location of the unit.

Use them less and less on the routine stuff as time goes on and your knowledge grows.

You file in small claims court to collect rent owed and damages.This is routine for landlords and although many will suggest that it is a waste of time it has been proven that at some time in the future many will come back to settle the claim.