Seth, what you've done is impressive no doubt. You built up a running youtube following to over 150K and live off it. Congrats! But now you've hit a wall. Less views, less new subscribers, poor content, etc.
IMO the issue is that your channel is all about you. It's way too much. Most people will not want to hear about your life or what you have to say every single day. You are way way too into yourself.
However you have a huge opportunity to bring your channel to the next level right as you can't run so it can't be about you. My advice is to bring on different athletes either track, road or trail. Film one of their workouts and have them explain their training. Maybe have them share thoughts on the shoes they run in. So many athletes could benefit from visibility on a platform like yours and you'll benefit in a massive way on having them on. Then you could cover a race they are doing to make it personal. Like you do with your bro.
Think about the people you've built the biggest addiences (podcasts). They have done it by having interesting people on..