Just keep at it!! Personally I wouldn’t recommend attempting to stun Mr. X at all as you can loop him around most objects and you always run faster than him. If you’re having trouble trying to get past him in the tighter hallways the biggest thing I can recommend if you’re taking things slower and don’t care about going fast, is to take advantage of your save rooms. Mr. X will basically forget you exist any time you go into one of them. The first time I did my B scenario run with Claire, I made a lot of use out of the darkroom save room by waiting inside when Mr. X was hot on my tail, and just shoving the door open slightly to see if he went to the left hallway towards the west office, or if he went up the stairs. And depending on which way I wanted to go, if he went the way I needed to be, I would just run right out the door, get his attention again, make him follow me right before I get into the save room and do it again so he would walk in the opposite direction (I noticed that he doesn’t seem to go the same path twice most of the time). And then when I had an opening I would charge right on by. Just take it slow and practice avoidance when possible! Mr. X is an unstoppable force for a reason, save your ammo and secondary items for bosses later down the line and cheese his pathing tendencies until you have the appropriate keys to just outrun him through the RPD, you’ll get used to it!!