okay I am not at my pc with maya on it but to merge the jaw in red arrow ..you need to go to edit polygons and then merge vertices ..that is what you do to merge. you need to do that aroudn the jaw ..if you watch the video it shows how to merge those two spots ...

also you see the purple line and red line ....those need to have a line put there ...that is where you use split poly tool. make a line there ...and that is located ..edit polygons and split poly ...then it will make two lines and you need to join the vertices by edit polygons and merge vertices ... when i say join you will have two seperate lines and you want to make them as one ..so join the two ends where the vertices are ....

the line with squigly marks on it ..you need to right click mouse and go to faces and just delete those .... cause you dotn need those ...they are just wasting space .... you can select more than one by holding shift key and clicking on the square and hit delete ..

save your file before you do any of this so you have a working backup of a backup