#1 I find myself speaking much louder when I don’t have hearing aids, or so my kids say. The fact that I can hear myself with hearing aids regulates the loudness and tone of speech for me, I think.
#2 That's true, the level of hearing affects your spoken level of response. I have no hearing at all but, my level of speech is perfectly acceptable and viable in mixed company, I've trained myself to do that, by watching closely other people to notice their body language and responses, if you see 'puzzlement' when you speak to people no matter how subtle it appears, then you know you are shouting or mumbling, or not understood at all, you can train yourself that way.
HOWEVER (There is always some unavoidable issue!), I cannot monitor background noise so get caught out then. I don't avoid such areas that is self-defeating but via a bit of humour or simply saying I cannot make you out because of that noise it's not so bad people will understand. I do think over-confidence with a hearing aid is an issue too it means you make less effort to follow assuming the aid has captured it all.
#3 Same with learning to lip-read, you need the aids switched OFF to manage that properly. Of course, UK classes insist you keep them ON, which I think is the wrong way to do it. There is no 'level playing field' between students either, so the those who can maximise their aids benefit more than those that cannot, even then, they can suffer if unfortunately, their aids are no longer of use to them, they have not attained the other skills they need to follow better, they left that to the aid.. Then and curiously, its a race to buy bigger, better or stronger hearing aids because they cannot cope with silence... and there are no areas to help them.