Here's a calculator that helps you size injectors: https://www.rceng.com/technical.aspx
but if you're familiar with sizing injectors for V8's then of course the approach is pretty much the same so that's probably old news to you.
Every question that you've asked has been discussed here very thoroughly through the years.
Additionally, a large portion of what constitutes standard staged tunes these days was developed on this very site, so there's lots of expertise here that can respond to specific and knowledgeably formed questions.
As example, you ask "what intercooler do I need", the answer to that is actually "a bigger one".
Beyond that, if you do some searching and ask something like "is ebay cooler xyz really worse than the $400 Genuine Saab unit?" or something like that, you're likely to get a few more bites.
Welcome to the site by the way, there's a ton of good information here.