A horse that won't stop is disrespecting you totally. Mine used to do it. When I ask for the stop (in rope halter), and he takes a while to stop or ignores me, I immediately one rein stop and then back him up....hustle his feet backwards.....until he takes about 5-10 steps (not 1 or 2)....ask for walk again....only let him go few steps. Ask for stop - if he doesn't stop on a dime, one-rein stop, back him up again. Keep doing it over and over. He'll soon get the message that if he doesn't stop when asked, he is going to have to work harder and go backwards.
If he keeps wanting to go back to the gate or his pasture, make him work harder as you approach the gate - ask for a faster gait before you even get to the gate. When he does the right thing, leave him alone. When he does the wrong thing, make him work harder. Only allow him to take a break in the furthest corner of the ring, nose in the corner. He sounds a bit barn sour, as is mine...he'd rather sleep than work :)
All of the above really helped me with my horse. He is a bit stubborn but super quiet and mellow. I have been mistaking his "mellowness" for temperment, thinking he is SO quiet and mellow....but honestly, he is being rude and disrespectful. I only ask him to "work" a few hours a week, so when we work, I expect him to work. Then he gets to rest. Good luck :)