That is a lot of work you are putting into that with very little to show for it. The problem is the hyper-focus that you are placing on Livestreams. While they are great for audience interaction they do not always translate well for discoverability. You should still be doing your SEO research and best practices and should have all that in place before you stream, but even then many viewers are often turned off by long videos and the more they drop off the less YouTube wants to share it out. Here is what I suggest;
For starters you should make your livestream unlisted after it is over. Download it and edit it down into multiple pieces of a single playthrough. Edit out the 'slow' parts. Give viewers a little more of a fast-paced experience and keep these to under twenty minutes apiece. Then set your SEO according to things that people could search for when seeking that game. Things like the scene, charaters etc are all things that people may search for. This is going to give your livestream an extra life as searchable content.
Also wouldn't hurt to give up a stream or two per week and focus on doing 'How-To' or 'Tutorial' videos. I know this doesn't sound fun, but as an obvious authority you have the ability to help fans of the game. people searching for assistance on getting through a particular event in a game (or the game in general) will often find your channel searching for tutorials and subscribe... only to become enthralled with your livestreams.
If you are unable or simply unwilling to make edited video content then you may want to break the mold and find a different approach to streaming in general. Maybe keep the streams shorter; if you stream for 30 minutes and make it searchable for a certain portion of the game then you can take a fifteen minute break and come back to stream for another portion of the game. This allows you two different searchable opportunities for that timeframe, double the views from anyone who comes back to the next stream, it leaves the viewer feeling like they didn't get enough and keeps them coming back (hopefully) and it increases the amount of ads being played.
If you are stagnating you need to change things up, regardless of whether these are the ideas for you or not. You need to freshen up your approach, bring the fun back and definitely figure out a way to incorporate more SEO strategy into your work. At nearly 1,000 videos you have a LOT of opportunity on the table. That wealth of content is not working for you the way that it should be. Finding a second life for that content in edited format or making your livestreams more digestible for an audience in search are two things I would highly suggest focusing on.
