Re: Help choosing the project and the designer/naval architect.
With that high of an import duty, don't import it to Brazil. Just create an overseas holding company as the owner.
Frankly I think you are going about this all wrong. You need to sit down and figure out what you want to do, where you want to go, and how many people you want with you, then look to see if there are used boats that meet your needs. A good used boat can be had for a fraction of the price of a new built.
Once you have a few years sailing, then go to a NA and have a custom boat designed if you choose. But frankly at this point I don't think you have a clear enough idea of what you need to really begin this process.
As for steel vs aluminium. It has been beat to death on this forum and others. But there is a reason that there are vanishingly few production steel sailboats being built.