Don't worry. The question is perfectly on-topic here.
When I read through your description of your process, I'm on the lookout for one single thing. And unless I'm missing it, I don't see it anywhere in your process.
You gotta add some resistance!
Every attempt you make at "switching it up" is fine. But at the end of the day, if you can do 30+ repetitions of something, it's no longer challenging enough for you to just keep grinding out hundreds and hundreds of repetitions, and expect the body to change. This is now something your body considers easy, and your body will simply get really good at doing 30 reps, and not feel the need to improve further.
You need to challenge your muscles in the way that makes the most sense: Get some extra weight. Give your muscles (not to mention your central nervous system) a new challenge.
Progressive overload
The phrase we always use for this is progressive overload. It's done in a few different ways, but what we refer to is the act of challenging the muscles either by, for example, adding more resistance to a movement, or adding more volume.
You've tried adding volume. And that's good. Eventually, you'll get back to that. But what you should try now, is to add more resistance to the exercise. Try putting a weight plate on your back, or a weighted vest on your torso. Get someone to stand over you and press your body down. Get someone to push you down with irregular intervals. Anything to make your muscles and CNS go "oh shit, we need to adapt to this".
Other exercises
Variety is key to any sort of progress with regards to strength. The fact that you're doing different variations of a pushups is great. And you should keep doing that. But you should also look at adding other exercises with similar, but differently loaded pressing movements are going to get your chest and triceps growing stronger, allowing you to do more pushups.
Bench press (in all its variation, be it on a flat bench, incline bench, decline bench, with a barbell or dumbell, be it laying on the floor) is an exercise you... I'll say it... you need to add. This exercise is probably the exercise that will allow you to move the most amount of weight, giving you that progressive overload I mentioned earlier.
Don't neglect the rest
You don't mention anything about how you train your other body parts. I will assume that you have a semblance of order in your training regimen, but I'll say this in case anyone else reads this: Don't let pushups be your one and only goal. Don't let pressing movements be the only training you do. Neglecting the rest of the muscle groups, and only focusing on 2-3 of them, is bound to lead you down a road with muscular imbalances, and chronic pain in your back, neck, and shoulders.
Some times, the best exercise you can do to increase your pressing movement, is train the muscles that help out, without you realizing it. A well-performed pushup is actually a very well-rounded exercise. While it does not train them very well, it does rely on your core, shoulders, back, and butt for stability. Make sure all of these are trained with the same amount of focus. In the long run, this is provide far more benefit to your pushups than any pushup-only training.
