That is way too much buzzing. Most people buzz to learn a close aperture lip setting and for a little lip strength. That takes weeks not years.
If you can buzz a double c then you should be able to play a triple c. There are a couple of reasons why you can’t.
1. Too muscle based. Air is the # 1 tool of a brass player.
2. Compression + compression + mouthpiece pressure = NO aperture for the air to go through. Basicly the tight muscular chops create such a small lip aperture that any other help closes and seals them. The pressure needed for a seal between the lips and the mouthpiece is not a lot but it WILL have some affect on the lips. Added to that the air column needed to play high is trying to blow the chops open. This actually blows them forward and that puts some of the embouchure inside the cup of the mouthpiece. This also closes the lip aperture. Lastly there is feedback added to your lips from the pressure wave inside the horn returning to your lips. This feedback from the horn stops at around a high g. The reflecting boundary is pushed out farther and farther as you ascend. And this causes a lot of players to have a break in range. When you add all of this together you have sealed them shut.
3. I was where you are now. You have all of the tools but you need to relax the chops so that the sound can be released. It is possible that you could accomplish that in a short time. It is possible that it also takes forever. This is now about overcoming the severe handicap of thought.
You know the facts. High notes need compression……. So you make an effort to add compression. Along with this some extra air support, a little more mouthpiece pressure. These things are what keep 95% of all high f and g players from being triple high c players.
At some point you have to not only stop adding pressure but actually take some away. That’s why Stevens and Mendez both told people of the ability to play a “No pressure note”. For the sake of a good sound you don’t want to go that far. You do want to pull the mouthpiece away and allow the lips to respond to the air. I use less mouthpiece pressure to play a double c than I do to play a g on top of the staff. If I use the same as I do for high c the note will NOT sound. Make an effort to pull the horn away from your top lip as you play higher.
1st lesson for range
Well the real key as always is to move the air faster and farther.
To keep abdominal reserve strength work on a natural approach below 4th space e . If you place your hand on your stomach and sing a g or c you will find that you do not tense your muscles. Check to see if you are using this same relaxed approach to playing. It only takes a day or two to learn this and you have more strength to speed up the air in the high c area.
For the mental part there are several points. Low notes are more non-directional than high ones. All you want to do is let them roll out of the bell onto the floor. Nice and relaxed using warm breath (haaa). The higher notes are directional and you want to shoot them through the horn to the back of the room. Use cold air like cooling soup. Music is an expressive art not an athletic event. Don’t go for records work on painting a picture.
As for the chops always set them for a g on top of the staff. This can prevent dozens of problems. Plus it is only an octave to high g over high c and an octave and a half to low c. Most problems come about because the set was on a low note like second line g. Now you have to muscle two octaves to get to g over high c. This is really a big deal. It is easier to set for the upper register and relax for the low notes than to set for the low ones and fight the high ones.
Make sure that you have a close (lips touching) embouchure then let the high notes out. To get a feel for what the lip needs to do in order to play higher try this. Put your teeth together and place a pencil between your lips. Let the eraser touch the front of the teeth. The other end (unsharpened please) will stick straight out in front. Raise and lower the end of the pencil using only the lip muscles. Raising the pencil takes lip compression (lip against lip) as do higher notes. This is also used by some as an exercise to strengthen the lips.
95% of the people that ask about endurance and range exert too much overall pressure (chops, abdominal, mouthpiece) and the notes can not escape into the horn. Relax the chops and pull the mouthpiece away from your lips as you ascend. The extra compression and force of the air column are already trying to blow the lips toward the mouthpiece. Pull away and give them some room to buzz. It may sound strange but I’ve seen it work hundreds of times.