SCARA 3D PRINTER- PROBLEM AFTER HOMING ARMS and Printing Model to Scale

Hi Guys,
I have built a SCARA 3D printer, it is completed. I have an aluminum frame structure, heatbed raises up and down like the Ultimaker.
The arms have there motors fixed on the top mounting plate. I have attached a top view of my printer with the critical dimensions.
I have been trying for a long time now on and off to make it functional, have used many firmwares from different users
Invent 2main, vitaminrad, and others as well. I edit the settings to match my setup.
The issue I am having is that I have no problem homing the arms to the end stops, the problem starts when they try to go to the 0,0 position
of where I would like my nozzle probe to start. Each firmware I have tested gives a different result, but never correct.
I have even switched positions of the end stops from left to right and back again , thinking that maybe that would be the problem
In other words a left or right handed Scara. but it isn't.
And just to be clear I never actually print with filament, don't want to until I know that the printer is setup correctly.
I test run a print through pronterface just to see the arms move, and see if they are printing the part accordingly.
what I have realized that if I was too attach a pen to simulate the print, it would be skewed based off the real print.
I am using motor pulleys with 20 teeth that drive the larger pulleys with 120 teeth, so that's a gear ratio 0f 6
microstepping is 16 , I come out with 53.33 steps for the X and Y motors.
From what I understand and have experienced, is that Marlin firmware is not suitable for Scara printers, unless someone
know the secret magic formula to make my printer functional the way I want it to run, I have given up hope.
So at the moment, I am using a code translator from cartesian to scara ( MPSCARA from Thingverse ) and then run it
through pronterface. I let the arms just move but not actually print, it seems to be ok, but the printing region is out of the heatbed area,
so that causes another issue- seems that there is no control from the homing end tops position afterwards.
I just cannot believe that this is so complicated , when it shouldn't be.
I enter the parameters in the configuration.h file correctly-there is no secret here, and theoretically it should give me the correct results
but it doesn't. do the kinematics need to be modified in the main marlin.cpp ?? what gives ??