[Solution Found! (at least for the time being)]
I think I may have found a solution to the problem. At least, for the time being it seems to work and I've been able to boot my computer, open ProTools and play music through the MBox from an old session.
The process was : System Preferences -> Network -> Thunderbolt Firewire and in the Configure IPv4 dropdown menu select : Off instead of using the pre-selected "Using DHCP".
This seems to have allowed me to boot the computer while having the MBox turned on.
I hope this works for you guys as well!! Avid support was utterly USELESS and I could've avoided reactivating my support/upgrade package and spared myself $300 in the process to buy something more useful...
Let me know if this works for you guys too and hopefully everyone will be able to get back to producing! <3