Their success is not directly from SEO but SEO amplified their word-of-mouth. They have also acquired brands that has helped but never ever forget - a killer solution to a killing pain point is what sets you up for success!
I would recommend Bookmark OS. It's not open sources but offers full text search, full page screenshots, and other neat features https://bookmarkos.com
I would say make it a priority to do a small thing every single day to make yourself feel better. Eating healthy, exercising, and sleeping well. Maybe even see a Dr. to get anti-depressants. I went on anti-depressants a while ago and it allowed me get my life to a place where I no longer need them and feel the best I've ever felt. It just takes time. I don't think experience will matter to a girl that likes you. It just takes time to find the right girl but you need to keep going on dates. I probably went on 40+ dates.