Hugo,.. as it is, there are many issues you really need to clean up... but I can close it using how I think it should blend... so, I'd suggest your break this up into boundaries (as if you are making a boat with panels) and knit.. you will not be able to shell.. you'd need to manually offset and trim/knit/surface cut..
essaieV3-zxys.zip 1.5 MB
Thank's for your answer.
I try to understand your SolidWorks schema answer, but like I'm not an expert of this software, I don't good understand how you doing your Boundary-Surface. So I ask if it's possible that you sent me the file SolidWorks please.