I am so sorry you're going through this, and you're stuck with this decision. Is the prodromal labour easing up at all and letting you get any rest, or are we still talking 41 weeks, 3 weeks straight of contracting AND previous big babies?
Hazarding a guess, I don't think the problem is that baby is big. I think the problem is that because baby is bigger, your uterus is fighting to get him into position and this process is proving difficult for some reason. It could be something as simple as a badly flexed head, or a nuchal hand. If I'm right, you're damned whatever you do: a chemical induction may work, but not on a hospital timeline because you're liable to end up with a c-section for FTP, depending on the nature of the malpresentation. Herbs/homoeopathics will probably worsen the prodromal without dilating your cervix. I would read Spinning Babies religiously, wear a support belt for your belly, because at some point those contractions are going to work. Baby will descend, your body will open and you give birth.
You can do this. We're here for you, we'll get you through this. Overthink things if you need to, sleep if you need to, but you are strong and you can carry this baby safely through this pregnancy and on out into the world. You've inspired me so much with your guts and courage on this journey through prodromal hell, don't give up now. The two of you will do this together.