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No need to be sorry. But I have probably bad news for you. In attempt to speed TouREP up there were some unsuccessful designs with 30 teeth T2.5 pulleys. That is almost equal to your 24mm diameter string spool. Seems to me that while 50 mm circumference pulleys are working just fine, 75mm circumference pulleys already produces so much momentum that the torque of these tiny motors is not enough. It may get better with the bearings we already discussed, but be prepared to change the design to use slightly smaller pulleys with circumference of about 50-60mm instead of 75.4mm you have there now.

You can try to use Arduino DUE that have 32bit ARM processor instead of 8bit ATMega architecture. Some versions of Marlin are tweaked so they can be compiled to ARM in Arduino IDE. From what I know Arduino DUE can be used with RAMPS boards as they have similar pins as long as you are not using LCD, thermocouples, optical enstops and motor drivers that needs 5V (DUE have only 3.3V instead of 5V on MEGA). In such case you would have to use DRV8825 drivers as they prepare their own 5V from motor power supply. Or you can go with RADDS or RAMPS-FD, as they are prepared to work with DUE with no such issues. But please take that information from me with a grain of salt and do some research on your own (as I never used DUE and I may got it all wrong).

Edit: Check this forum for what have to be changed on RAMPS to make it run with DUE: http://forums.reprap.org/read.php?219,479626,page=1