I wouldn't recommend stealing Brooks Brothers' names. Medium spread would be a good name for your "cutaway." If you call it a medium spread, "wide spread" might still make sense for your cutaway collar.
"Single link cuffs" on these forums is most typical, but I've heard them called just "single cuffs" as well. Link cuffs can be either single or double. I've been communicating with people about clothes online for 8 years and I've never heard of "link cuff" used anywhere to only apply to single cuffs.
It is called a single link cuff to differentiate it from the more common double link cuff, usually just called a double cuff or French cuff. Just "link cuff" doesn't necessarily mean it's a single cuff.
I too noticed they call a spread collar a "cutaway" and a cutaway collar a "spread". It's indeed confusing when they call things the wrong names. When I ordered shirts from them a few years ago I got the large cutaway collar, which is a great classic spread with my perfect proportions. The only thing I don't like about the collar is how the band isn't angled or curved down in front.
I don't see the point when I can just open my closet or my drawers. Everything is sorted so I know where everything is. I've made a list of things I'd like to get, and I have digitised catalogues of other things. But I've never done it with my wardrobe.
Pretty much everyone puts 4 buttons on everything now. Some Italian tailors like 3 buttons, and a few English tailors also do three. Some American do 2, and in the 60s it was popular to have only 1 button on the sleeves. There are no rules to this.
Make sure the sleeve length is perfect before the buttonholes are made. Some people get the suit shipped with the buttonholes already in, and that's a big mistake.
It might be best to start by going to a store. I have a great pair I got a few years ago from Brooks Brothers, though I don't see them on their website currently. The best to start out with is dark brown leather lined in cashmere. They will keep your hands warm. I only wear gloves when it's cold, so I prefer lined gloves. I like dark brown because they look good with most business dress.
The places where a point collar becomes a spread collar becomes a cutaway collar aren't fine lines. What do you mean by a "classic collar"? Like a moderate spread collar? This one is a spread collar, and a fairly wide spread collar at that but not a cutaway.