As a MH owner I can attest they are not a very good cutter, however, they can be tweaked to cut pretty decent for a hobbyist. Software will not help with your problem of cutting funny or vinyl slipping. The only way software can help the cutter is if the software has the ability to set blade offset and over cut. Adjusting blade offset will square up the corners and adding a bit of over cut will ensure cuts close completely.
I suggest we pick one problem to start with and trouble shoot it, then move on to the next one. Setting blade depth, speed, and pressure will be the first steps to getting the cut right. On mine I have my speed set to 120 and pressure to 70.