i can get all the way to that one pit where you stand at the edge, and a monster is running back and forth below you. the only way to get to the other side, is to jump off the ledge, run to the other side and pull your self up. you have to do all this before the monster gets you. but if you run too fast you'll hit the wall and fall over, instant death. so what do you do?

I assume you are talking about the first Scrab chase in the secret area after you leave Rupture Farms? Here's an excerpt from a walkthrough:

"As soon as you appear, chant to open your escape portal below. Drop down and run to the right and turn and retreat as soon as that Scrab sees you and shrieks. Run back and jump to the ledge and pull up. Now get the attention of one of the Mudokons and when the Scrab is facing the left wall say "Follow Me" and start running to the right. Jump the gap in the next room and jump the two gaps in the room after that. On the next screen jump and grab the ledge and pull up just as the angry Scrab arrives. As he paces about in frustration below you can chant to open the portal and send the first Mudokon on his way. Wait for the Scrab to face the right wall then repeat the previous run in reverse ending up on the left ledge this time. Get the attention of the remaining Mudokon and repeat the process all over again. After you have rescued Mudokons 30 & 31 wait for the Scrab to face the right and run back to the left and this time hop into the portal which you so wisely opened in advance."

nah its before that. this is simply a one screen puzzle, where you are standing on a ledge, and below you is a scarab running back and forth. you can't jump all the way to the other side though, so you have to jump into the pit, run to the other side, and pull yourself up without getting eaten by the scarab. I'm sure your walkthrough will cover that.