Ok, looked through the manual, watched the video on homing and can't find where I tell mach3 to back off from the homing switches by x amount...
Anyone have any ideas?
You don't, this feature is programmed in.
When you have a home/limit switch set correctly and issue a home command on that axis, the axis should move towards that switch at a rate you set on homing/limits, when it hits the switch the switch opens and mach stops movement, reverses and moves away until the switch closes again, thats it as far as i understand things.
When you said earlier your axis was hitting the frame before the switch does seem to indicate a very poor build/design as that should never happen, glad you got that sorted.
As for positioning the work, at switch on I home my table to set machine co-ords to zero on x/y as z is not homed on a plasma. Then I place my material wherever and align the cutter with the corner of it and zero my work co-ords, now my machine knows where its axes end and also where my material lies. In my Cam software I have an image of that sheet and I place the parts to cut exactly where I want them, as the sheet gets used up, I just remove the cut operation from previous parts but leave the part on the sheet so i can see where material has been removed previously.
It sounds long-winded but in reality it means I can use my material more effectively by keeping part-used sheets for smaller jobs and fill in the gaps when needed later, all the sheets are numbered as are the cut files to match, all the jobs are placed relative to the corner of the sheet which i use to set my work zero - 0/0.
I have no idea what cam solution you run but with your fixed strips of wood this method might work nicely for you too probably. I can take a part-used sheet off and reset the entire machine, replace the sheet and continue using it very easily as long as i set the work co-ords accurately.