A few pieces of info that would help offer better help: What are you streaming? What's your schedule? What are the specs you are streaming at?
First thing is that it's only been a week! I'd turn your perception around a little and think of it more like "This is awesome! I just started and have already had peak veiwership in the double digits!". Seriously, growing an audience will take time. (something something Rome not built in a day something something)
If you're talking all the time, keep doing it, that is a good thing. Keep talking even if its only to Nightbot. This ties into your first question about what keeps people watching.
People want to see your reactions to what is happening, and to interact with you so keep up the talking.
DO NOT CALL OUT LURKERS.
Seriously.
If you don't have a schedule, make one and stick to it. This matter a lot more than you would think. I myself tune in at certain times because I know thats when my favorite streamers generally start up.
As for the overlays, thats one of those things where you're not going to please everyone. I will say the trend has been to lessen the amount of overlays the last few months.
Face cams are generally a good thing. I know Lirik and a few others don't, but a cam certainly helps people feel interactive with you because they can see your reactions.
Obviously the quality matters, but people aren't as harshly critical of the video quality with smaller streamers as they are with audio.
Bad audio (humming/crackling/etc) will drive people away, but you sound like you already understand that and are working to fix it.
All this said, just keep streaming and having fun. If you're having fun on stream, you will find a following. Don't get concerned with how fast or slow others grow, there is an inherent RNG to growing on twitch (right game/right schedule/etc) that you just gotta live with and the only way to live with it is to have fun doing it.