Good list and covers the fundamentals.
Yeah, those points might be a good check, but even if they try their best, they might still fail with their project. This does not mean they scammed you. They just failed to deliver. The most important check is the team and who are involved. If there are well known developers, then high chances it won't be a scam. If they remain anonymous, just stay away from it.
This is the key advice - there are so many projects that if it doesn't solve a unique problem or address a gap that is useful to address it might still fail. Not because the team intended to scam, just like any business the idea was not something the market could get behind. That said
...If they remain anonymous... is the biggest red flag. Why would any team who genuinely wanted to make a success of their project, to address a real need and see future success - stay anonymous?
Sure, they might be working on the project part-time subject to raising funds, they may be concerned about also being scammed if they are successful and known. They can say this and again be open about it. Overall though, the team should be transparent in their presence, communications, progress, updates and yes - problems and roadblocks. If they are, then some inexperience, a need to polish the concept, a few gaps in the white paper, etc. are all forgivable. Hiding, not so much.
CBF