Thanks for the replies, guys. I've gone ahead and reset the settings to default and then tried a print that was already on the SD card that came with the printer- it printed fine (the head moved to forward-left position, as it should) and printed just fine- the other files still have the same problem, so it must have just been those files- a bit more on that later.

As far as the firmware I chose, it was the FlashForge Creator Pro & X w/ ATmega 2560 as that was the closest thing. I'm not positive on what Replicator clone it is, plus when I plugged it into my computer the Makerbot software identified it as a FFCP, hence the choice.

Rundown of things that are working:

A) it looks like you were right- Cura was a big part of the problem. I made sure that the preheat setting being the default temp. for prints was turned off after resetting sailfish, and now the files print at whatever specified temps I chose (except the ones sliced in cura, they still try heating up to very high temperatures).

B) Heating up doesn't cause the extruder to actually run and extrude plastic the whole time (again, except the cura files).

C) Canceling prints is a little tricky, because the preloaded files cancel and return the printhead to home as it should, but a new file I tried slicing with S3D doesn't. More on that below.

Going back to the strange homing issue after canceling prints- I tried starting and canceling a print that came with the SD card. It came to the front-left just fine, heated correctly (and the bed didn't take nearly as long to heat up), and i let it run for maybe 15 minutes, and I canceled it, and the print head went to the home pos. correctly. Here's where it gets a little bit more confusing for me- I'm trying out S3D to see if that works, as I read that it also can slice and output X3G files, so I thought that perhaps using that could cut out RepG out of the process. I tried using the same file as before- a model that one of my friends made (and I cleaned with netfabb cloud)- but now it's acting a little more different than before.

Now, with this new file, it doesn't even bother homing or repositioning any of the axis before heating. If I were to move the build plate a couple inches down or move the printhead around somewhere and then starting the print, it would all stay where it is, heat up, and """begin""" the print as if it was in the correct area. I'm sure that's some setting within S3D, but I can't locate where that would be. When I cancel this print, it just stops right where it is, instead of moving to home like it should. This confuses me a little, I guess because I'm not sure about exactly how the Cancel operation works. Does it just run the end script in the Gcode (or, in this case, x3g) file, or is the cancel built into the firmware? Based on what I'm seeing, it looks like the former.

As far as it seems, the printer is doing everything correctly so far, and the problems all lie in the files I'm trying to use myself. If it turns out that the problem above is fixed via some S3D setting, I'd be really glad- S3D is what I was planning on using. I guess I'd be a little disappointed if I'm limited to a specific slicer, but such is life.