His wife was also named as a party on the lawsuit, so I told him that if he didn't pay by a new deadline, I was going to have his wife arrested at work and brought to court.

It's "Notice of lis pendens" and it basically means that there's been a lawsuit filed against the property usually when there's title dispute.As an investor, don't get emotionally attached to properties because it will end up costing you more money when you can't just walk away.

It is easy to do because it seems like you can get away with wider spacing etc, but that is a quick way to a lawsuit if it fails. 

If fix the pool, I cannot charge additional rent as I am already capped and I will be stuck with maintenance costs and I can't help but think that if someone drowns in a functioning pool and if it turns out that the landlord could have done "something" whatever that "something" is, he may be on the hook for a major lawsuit.

I'd get going on a loan now.FWIW, a paid-in-full property is a target for a lawsuit, and well-leveraged property is much less attractive. 

Tenant A said she will press lawsuit against Tenant B.

If you own the property in your own personal name (not an LLC or corporation or trust, for example) then you can file your own eviction lawsuit. 

All of them need to be used in conjunction for a comprehensive structure giving you asset protection.Now some people will tell you they are not using insurance nor any asset protection at all and have done well for years, some other will tell you horror stories about losing their shirt on a devastating lawsuit.

I am not sure why anything should have changed since it's not used anymore after 1995 and there was a $1B lawsuit in 1999 plus it's not in the building code anymore since 2007 or so.

Why not try hiring a private detective to follow the kids home and then turn them into the Police (file a lawsuit against the parents, and a restraining order against the 14 year olds).You only need to find the home of one, and he will Rat Out the rest under the (perceived) "third Degree" questioning by the Police Officers.They might still throw rocks, but at least you can get a handle on it some what.Maybe a witch lives there, or a monster, or a ghost--who knows--it's kids..(???)