Would an ENT be able to perform a complicated septoplasty due to previous accidents / procedures?

Typically, anything involving the septum is going to better treated by a facial plastic surgeon or ENT doctor rather than a plastic surgeon.

As you have had previous surgery due to trauma, I would recommend that you see a surgeon who is experienced in facial plastic surgery and nasal airway surgery. These can be either ENT or plastic surgeons who have done additional training in facial plastic and reconstructive surgery. Your specific situation may be difficult due to previous surgery/trauma and the possible need to support your septum with grafts.