Right, I've asked. If it's been formally granted in a Deed (which I would assume it has in a new build/modern property) then a ROW can never be lost, until it is formally released (also by way of a Deed).
The advice at this end is that if you sell, you would have to disclose that you are not exercising the right of way and that there is a potential dispute over it. So you are better off making this formal and asserting the right of way. A purchaser would prefer this - they buy a property where there has been a dispute but it's been resolved, as opposed to buying a property where a dispute is brewing and unresolved. This advice is from a conveyancer.
If you were a client I would advise you to follow the instinct you have already expressed, and which I agreed with in my last post. Wait a bit, then write a conciliatory and apologetic letter explaining everything. Wait a bit more. If the behaviour doesn't improve, go to a solicitor (using your legal cover under your household insurance which virtually all policies have). I think you might have to put your insurer on notice now of a potential dispute.
Make sure you are recording everything: a daily diary (eg iPhone Notes), dash cam recordings, photographs of the ROW being blocked every day by cars, and contemporaneous notes of any confrontations/other ROW blocking that you can't record/photograph for whatever reason (eg you shouldn't photograph children).
Of course, if the behaviour as it is now does not let up at all then you might have to rethink this and ditch the wait and see part of it.
Asserting the ROW won't stop stupid and aggressive behaviour like DM ranting at your gardener.
If the harassment continues, then you need to follow this up with the police, but also try to get some evidence of it (because they'll probably make counter allegations, as they have already done). Google PIN (Police Information Notice). Because the police guidance is that Protection from Harrassment Act complaints have to be prioritised, the police are inundated with low level stalking/harassment complaints. They have developed an informal procedure for dealing with these - they visit the offender, inform them of the complaint, explain the provisions of the Act and that if the allegation is true and the behaviour continues then they will be committing an offence and may be arrested. They then hand the offender a piece of paper (the PIN) which records all of this. The PIN is then entered on the national and local police data bases, where it stays for a year.
I often post on these forums about PINs. As great as they are for someone like you, they are also open to extreme abuse (for instance in domestic disputes where one party can make up allegations and then jump up and down when they are next in court saying "look, the police served a PIN" - even though the PIN procedure involves no investigations or findings of wrongdoing like, for instance, a caution does - a Home Affairs Select Committee has investigated this and made certain recommendations) - but that is another story. For you a PIN would be a great idea. Once it's served, if the behaviour carries on the CPS may well prosecute.