you don't need timestretch, and man do I take issue with saying the 2kXL is more simplistic to use. Never found that, I think this is his first MPC, and those problems would exist with any gear.
You should do what detail said, thenjust mes with the BPM.
And go to Timing correct, and change the TC setting from all the different values and check them out. Get it to 1/8 to hit your loop at the beginning of the sequence, then set the tempo really low, like 60, then listen to the loop, it should finish (depending how long it is) then silence until the sequence loops again, then the loop will start again. Now turn up the tempo and the silence will be less and less, until you get the sample looping nicely.
Man, you were changing the time signature, don't do that!! No reason to initialize sequence, it is so easy to edit and copy or insert to set up your sequence. it is really only needed for time signature changes.
Now, seeing this, you need to READ THE FARKING MANUAL!! like 8 times! Take it to work and read it at lunch, or on your commute if you don't drive to work, or read it at church
you are making it much harder than it is by trying to go to fast, slow down and learn the stuff well.