The Maximum Speeds seem very low for a CO₂ laser:
- X = 200 mm/s
- Y = 150 mm/s
For comparison, my 700×500 mm OMTech has 500 mm/s for both of those.
So, yes, it will look like it’s going slowly, because it is!
The acceleration values are also low. My machine has 10000 and 3000 mm/s² for X and Y.
AFAICT, the scanning offsets should be positive numbers, not negative. In any event, the machine was not running any faster than 200 mm/s, so you’ll need to re-do those measurements after uncapping the speeds. This may also clear up the “faded” lines and off-center engraving, as adjusting the turn-on time in the wrong direction could produce truncated pulses.
The 3.0 mm home offsets seem large. Does the machine have mechanical home switches? Does the home position leave 3 mm clearance from the switch positions?
That is 100% guaranteed to be a mirror or lens alignment / cleanliness issue, because there are no software or firmware settings along the lines of “get weaker over on the right side”.
If it’s much worse in the far corner from Mirror 1, then a “fourth corner” tweak is in order.
Unfortunately, because you cannot access the settings of the old controller, you must reconfigure this one from scratch. The fact that “it used to work” suggests getting the details right will improve the results, but we must work from the evidence at hand rather than recalling The Good Old Days. 