It might be a good idea to ask yourself the suitability of the size of some (most) of the food items that you listed, in relation to the size of the sea dragons.
Some of these questions could be easily researched and thought out yourself. Not that I'm discouraging you from posting, because I am not, that is what this board is here for, but PMing people to answer hypothetical questions about whether microscopic "reef bugs" would be a good food for large, rare, difficult to obtain syngnathids might not be the best use of your time if you're trying to create a primer. Personally, I would like to see the thread stick to actual experiences with the syngnathids, and known care requirements, rather than hypotheticals and what-ifs, but maybe that's just me.
It is my opinion that whenever venturing into an area that you are not familiar with (be it keeping a new animal, or anything else you would do in your life), that you should first build a base based upon the experiences and advice of others who are more experienced than you. And then, once you are experienced, then use what you know to make educated trials and "experiments". So, rather than asking if they could be kept at warmer temperatures, or fed unorthodox foods, I'd like to see more information on what is being used successfully with them now. Am I explaining myself well?