M.P.
I suggest you talk with a police officer about your concerns. Call the non-emergency line and ask to speak to an officer. The police can tell you if they have a criminal record but you'll have to have their full names. They can also advise you on what to do. It may be that your info will fit in with what they already have which will help the police to catch them, tho they probably won't tell you that. They can, at the least, do more drive bys. My department has reserve officers who do frequent drive bys when they're requested.
As a retired police officer I suggest that you get to know them. It's psychologically more difficult to steal from someone you know and like. Keeping them at arm's length definitely won't help and may make them more likely to continue with their crimes. You have nothing to lose and something to gain by getting to know them.
Definitely report to the police all suspicious circumstances. It might help to have your neighbors see the police at your house.
After your SWH: I'd check with the bank. Most homes, taken back by the lender, are left empty. Ask if they know there are people living in this house.