For full tool radius comp, the profile should be the final profile. You have programmed an offset path, which basically does not require comp.
I backplotted your code, then offset the result to give what I think is the full size of the slot as it would be drawn. Then, I generated the following code. Your D3 value will be .5 to start:
T3 M06 ( 2FL SMT 1/2" CARB REG LEN 1.0")
G90 G80 G40 G54
G43 H3
S7500 M03
M08
G00 X-0.54 Y0.7602 Z0.2
Z0.05
G01 Z-0.25 F24.
G41 D3 X-0.55 F48.
Y0.414
X4.03
Y1.086
X-0.55
Y0.7602
G40 X-0.54
G00 Z0.2
M09
M01
M5
G00 G49 Z0.
G00 G53 X-20. Y0.
/T1 M06
M30
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)