Could Othello have protected himself from Iago’s schemes?

Yes, of course. Othello allowed his jealousy to betray him. He allowed the one flaw he had in his character to leave him open to manipulation. Rather than think of all the reasons he should believe in his wife, he completely disrespects who she is as a woman. He needed to conquer his jealousy rather than let it be fed by Iago's schemes.