What a lot of people do is just ignore responses they don't find helpful, especially if you tell them that you don't find it helpful and they respond again in a way that doesn't make you feel they understand what you are saying. You don't owe it to anybody to explain yourself, and are probably more likely going to be derailed from getting advice you will find useful if you get sidetracked getting into a debate about it. You can ask for specific advice only all you want, but people will say what they think might be helpful, or ask things to clarify your situation so they can give the best advice possible.
Sometimes other people's communication styles are just vastly different than ours. I didn't think he was being condescending, or anything at all for what it's worth, just trying to be helpful coming from his own experiences. When you ask for advice on public forums, your responses will run the gamut and you can't really do anything about that.
"Do I need to ask for people to not assume DH and I want to explore poly to its fullest limits or that we both necessarily want other lovers" Well, yes, you probably do if you want the advice to be specific to that goal - or at least state that you are only asking about having non-sexual relationships. #1 not everybody will read all the posts you have written before responding to a thread, and #2, right or wrong, people may assume that if you're talking about a romantic relationship that sex is either a component, or something you would like to be involved at some point (also lots of people don't read follow up clarifications, so if you say it further along, they might not even see it and only be responding to your original post). I happened to make that assumption myself from your first post.
Anyway, I hope misunderstandings dont keep you from feeling free to post and ask anything you want. Hopefully you aren't still worrying that it's bad you aren't comfortable with him having the same sort of relationship you do when he says he is fine with it, but if you are, that is a good thing to work on in either individual or joint counseling. Maybe you'll find this article