Yes, I think that kind of force is what it takes. Also, using a harder washer under the bolt is a good idea.
It's interesting how much the thread friction reduces the axial force. You would think that a smaller thread pitch would increase the force a lot, but it's only modest, because of the friction. Making the bolt smaller in diameter helps most, because it reduces the friction. So, there's a trade-off: theoretically more force with a smaller bolt and nut, but the bolt and nut are more limited in the forces they can handle.
This is a lot like removing tie-rod ends, I think. My tie-rod remover alone usually won't remove them, but I tighten the remover and give the thing a whack with a hammer, and the tie-rod end invariably pops loose.
I bought a pair of axles and hubs while doing the TR4A restoration. They were advertised with the hubs attached. I told the seller that' I'd buy them if he could get the hubs loose. He sent them to a shop, which cooked them in the hot tank for a few days, and then got them apart (not sure how; probably a hydraulic press). I don't know if the hot-tanking helped, but at least they were clean when I got them!