No remarks on the full solution/ CAT5e question?

Well,

Setup seems fine I think but it probably wouldn't hurt to have a 8 or 16 ports gigabit switch and extra pairs of cable for future. And probbaly I'd prefer a modem -> switch -> wireless router setup if switch was at least 8 ports assuming your modem is also a router.

And for questions,

1 - To be honest, I have no idea at all

2 - There are some network cables made with aluminum instead of copper for cost reasons but they rarely write such thing imo but usually sold as saying they are copper. Stripping some cable then stripping copper yellow patina may reveal that it's actually aluminum if that's the case. Other than that we generally prefer Cat6 so not sure of actual performance.