Whoa. Immense strength bro, you're stronger than me. So yes, this is very good, what do you mean "if this is any good"? There's three things that I can think of for the muscle mass gains:
-Nutrition: Since when you gain weight your BMR will raise so your TDEE will raise, you will have to eat even more calories in order to gain new muscle. So, try eating 200-500 more calories than you are now if you're not seeing that good results. Muscle gaining also takes a lot of time so patience bro. A transformation takes a lot of time, look in years and not those false stuff like 90 days, most of them already knew what they are doing and probably had muscle and maybe lost it and regained it fast or something like that.
-Workout: If you're doing something that's easy, you won't progress, you probably know this already. So 16-17 pull ups is working a bit more on endurance as you know the typical bodybuilding reps is like 5-12, so maybe do a harder variation or add weight, or put more time under tension or do 1 and a half reps, you can do a lot things to make it harder.
-Genetics: Yeah, like not everyone will gain muscle equally, one person might gain a lot more muscle just doing the basics than a guy who can do levers, muscle ups and so on. Don't get discouraged.
I know how annoying plateaus or little-to-no progress can be. But that's a part of growing, many people will give up, you don't and GO GET IT. Try eating more calories, should help I suppose, you should get advice from someone who is bulking since I'm mainly cutting +minibulking, kinda like both at the same time.
Front lever is a matter of lats & back strength mainly, also core but if you can do dragonflies raises your core is pretty much ready. So you have to have a good base of pull strength which you have, now there's a few progressions: tuck, advanced tuck, one leg out, advanced one leg out, straddle, and then full front lever. That's for both raises and the hold. Once you can hold a progression for a solid amount, say 10-20 (+) seconds, go to another progression. Just know that it takes time and you should still be doing other pull up exercises. You can also do negatives to a hold of a lever progression, help a lot. One arm pull up is a very hard exercise, I can think of a few progressions: One arm assisted pull ups, One arm pull up hold (you can learn it by Typewriter pull ups), One arm pull up negative, and eventually you should be able to do it with time, I don't know I can't do it I just know the progressions lol. Also stuff like one arm negative to half and trying to go back up might help once you're strong, and then lower and lower.. Yes you can do the CU requirements bro, you sound like a beast haha!