Dissertation - What design should I use?

I am studying Clinical Psychology and I am currently starting writing my dissertation paper. I have some trouble defining the most suitable design for testing some hypotesis. Consider the following hypotesis that are in the screenshot below. Considering that I am targeting a non-clinical population, and one of the variables would be the severity of borderline features/symptoms, what is the statistical design I could use and how?



Fortran must die
I suggest (as someone who did a dissertation in a way I regret now)

Talk to your committee especially your supervisor
Do a literature review of how others have done this.

Consider carefully your own statistical knowledge. SEM might be a great way to do something, I am no expert in your field, but you have to know it to use it. Learning it for a dissertation is dangerous as it is very complex and takes years to know I think.

If you don't have an extensive background choose something simple like regression or ANOVA (or the simplest method you can use).
Thank you for your reply! I am familiar with mediation/moderation and ANOVA, which I used for my thesis paper. The thing is that design doesn't fit with these hypothesis considering that I am targetting different levels of symptoms and I am analysing the outcomes.
The supervisor is challenging me and making me think the design by myself. I will have to give it some more thought haha