Concerned x Worried: Como utilizar

Hi folks....
I'd like you to help me, cuzz I've got some doubts in some simple stuff...
1° -I was thiking...what is the main difference between "worried and concerned", is there any difference in using them?
Maybe any meaning difference?

and there is a part of english that I already know how to use, but I don't know how to explain...
2° - what is the best way to explain the using of 2 verbs, one in present simple and the other present continuous...
kinda "Stop Smoking"..."keep watching"... and so forth

3° - and the last doubt...there are some verbs that adding "A" to the beggining, they get the same meaning of adding "ING" to the end.....( I THINK SO, I'M NOT REALLY SURE ABOUT IT )
I better give some samples to be clearer.
He's waiting for you....He Awaits you;
They are sleeping... They are asleep;
She is waking up....She is awake*. ( actually, this one I'm not that sure that could be used like this )

Thank you guys...and I'm sorry for making these big questions in the first time I come here