I am so, so sorry you're having to deal with this. What a pain, and good for you for continuing to BF your babe. I bet he's doing as well as he is because of all your good milk!
I know adults can get IV iron. It carries some risk of reactions, and I'm not sure kids or babies can get it, but it might be an option to discuss with your hematology team.
I totally agree with the PP who suggested that a compunding pharmacist might be able to mix a tastier formulation for him- although no matter how you slice it liquid iron is pretty gross.
Also, honestly, if I were in your situation and I really needed to get that oral iron in b/c there was no other way to get it and we were both getting way stressed out, I might try a little cereal. I know you said you wanted to EBF for a year and I respect that, but you may want to talk to your team about the risks of ongoing iron deficiency anemia versus the risk of starting solids (only just a couple of tablespoons of cereal to mix the medicine in). I say that with the utmost respect for your situation and decisions, but as a healthcare provider and a mom of 3 who also knows that sometimes the best plan in any given situation isn't what you'd do in the ideal situation.
Good luck and hugs to you.