Luffy hit him with a golden knob on a golden bell, plus his accumulative strikes are able to hoist up a city. He's not as strong as he is now, but the biggest difference between then and now is that Luffy's Gear 4 can do it in one punch while base took multiple vigorous punches.I doubt we've seen his best but I think we got a good idea of the range and I don't think he measures up to 10 days based on the way back then showing. He may have grown but Luffy was a lot weaker back then and he still managed to wear Enel down.
I'm not sure about the storm clouds that needs some more research.
Because Akainu's a logia and Enel doesn't have arm haki to make his attacks contact with Akainu. As far as I know lightning wouldn't do anything to magma on a purely element level so without arm haki Enel has no way to cause impact on Akainu.
I think Enel is very durable for taking those hits and getting hit by those massive golden items then later escaping. It's going to take more than a simple buso haki punch to take him down if he was smashed by a golden bell (besides people like garp, I don't think any ordinary buso haki can break a golden bell).
Enel can give him a little challenge but I know he'll ultimately lose in the end. I brought up the storm cloud thing because Enel has dials too.