1. Do reverse engineering, use tool to find out where your competitors get links from.
2. Build backlinks, especially high authority links, don't use low quality links.
3. How many backlinks you need? It depends on your niche, so reverse engineering is very important to evaluate. As I see in some region(not Indonesia), most of high rank gambling websites build many own blogs in different domains, and linking back to main site. Which is similar as PBN.
4. Every high rank gambling websites(every one), they all have good contents with good article strctures, clear topic for every post, contents also supported by images.
5. In my opinion, your CWV and PSI don't need to be perfect. Contents and links are priority.