Why does Franky have such a low bounty? Does anyone even go after bounties?

[Warmmedown]

He knows how to build Pluton. Isn't he incredibly dangerous for the WG? Putting a higher bounty on him would incentivise pirates to try to kill him. Is a 44M bounty enough to get anyone powerful to go after him? Robin had 79M.

Does anyone even go after Grand Line bounties? Katakuri could have made some quick cash visiting the SHs on the way to Dressrosa. So many from the New World could go to Paradise to make money.

 

[SSJ2]

Is it even possible to sail backwards without having eternal log poses to every island? The log pose only points to the next island iirc.