You can click "make a hub about it" and answer these questions with a details hub.
There were a number of times when I began answering a question and before submitting it, I realized I typed quite a bit. So instead of clicking "submit answer" I copy and pasted it into notepad. The clicked to make a hub instead, and copy and pasted my answer into a text capsule instead. Finished it off with more elaboration where necessary, completed the hub with all the required items, such as summary, tags, etc., and published it.
So keep that in mind if you find you are entering a lengthy answer that may server better as a hub.
As for your other questions, If you already have a hub, I am not sure it is proper to link to it. Maybe someone else knows the answer to that. I avoid it myself. But I would make a comment that I wrote more on the topic and people can go to my profile if they want to find it.
As for html, no that is not allowed on HubPages.