It sounds like the PM was trying to do a quick, lower cost job to save money, and while it didn't meet your expectation, I feel it could have been prevented with better communication.

If it does have to go through your property-make sure they have a separate line-nothing is shared to prevent a repeat where their sewer backed up in your basement and they pay 100% for their line and you pay 100% for yours-more expensive, but better in the long run-and you hopefully get control of where it goes as they should twin the two lines (two pipes next to each other) to reduce digging.

You can at least prevent/reduce the credit card letters by asking the credit bureaus to stop selling your address and by putting your name on the direct mail associations "do not mail" list.

Credit is important to getting loans and getting good interest rates and may even prevent you from getting a loan in the first place.

It was installed using the same bolts used on stop signs to prevent it from being stolen or removed. 

To address this many states pass laws concerning the sale of a controlling interest in an entity... so while you may think you've avoided paying transfer taxes that is not always true.People also do this to prevent a property from being re-assessed in jurisdictions where a sale would typically trigger that.

Now read, ask and learn everything about private- and hard money lending First to prevent your cash from evaporating.

Hopefully Texas will follow suit so you will be prevented from taking advantage of more people.   

Might be something else in your contact that prevents renting, but a prohibition against assigning the contract does not. 

To prevent those items I suggest lots of tenant screening questions (back-round check, credit check, eviction search and income verification) and an annual maintenance plan on your properties.