put the near fields further back, and/or use Auralex foam underneath them - less rattling and booming from the desk
If you don't use a sub, the guitar sound will be much weaker compared to real amps, and you are likely to blow your drivers
Although a very expensive and attractive monitor stand, the Axefx mk2 is too noisy for normal studio volume levels, so having that so close to you may well cause problems. Again Auralex underneath it to decouple it would be good, but won't silence the fan
There's no more EMF noise in the monitor than the digital stuff in the Axefx, and it's a sealed metal box, so should be no interference issues. Running unbalanced signal wires near your monitor leads might cause minor issues
Those dinner plates and glassware behind your monitors would soon be rattling if I was using your gear!