I don't see why people are freaking out about peoples strength when franky blew him back. we saw his coup de vent a few times before.
Once shown destroying that huge steel/iron arm ting at shipyard. First shot bent it bad, second it knocked it over and what not.
Second time it was used it knocked out Zipper Mouth
Now we see him shoot from decently close range direct hit in chest on Kuma (robot). He was blown back and hit the nearest tree. The tree didn't blow apart or anything, no damage as we can see. (Kizaru blew up an entire tree by accident it seems)
And Kuma seems to be fine at the moment too. And what does Franky have like 4.5 liters or something of cola right. And coup de vent uses 1.5 from what i recall. So he used a 1/3 of his power and Kuma (robot) is fine. So it ain't showing he ain't super strong, neither is is showing he is super weak. Since he did send Kuma flying.