I can answer all of your questions with one response. I love singing and I can give you the insight on what I was taught at my performing arts school.
1.) How do I increase my breath to sing a long note, tones and have better breath support/control?
You can increase achieve all this by simply breathing from your diaphragm. Think deep and dark and imagine reaching the bottom of your stomach when inhaling air. This may not work the first time around because singers have to build strength in their diaphragms over time. I suggest doing some breathing exercises along with your vocal warm ups (going up and down the scale) while breathing from the bottom of your diaphragm.
side note: You’ll know that you’re breathing correctly from your diaphragm when your chest DOES NOT rise. Only your stomach should expand forward.
1.) put a piece of paper against the wall and hold it with your finger, take in a deep breath using your diaphragm (not your chest) let your finger off the paper, and see how long you can keep the paper sticking on the wall by only blowing on it.
2.) lay on the floor, place hand on your stomach, close your eyes, imagine deep down, and slowly inhale from your diaphragm, keep practicing for a minute at a time. (DISCLAIMER: YOU MAY GET DIZZY) but if you do feel that, that means you’re doing it right.
3.) sing with your jaw dropped ( especially for classical/ choral music)
* It took me about three to five months to achieve diaphragm breathing so don’t feel impatient, it gets better with time, age, and practice. But, I GUARANTEE you that, it’ll help your breath control so much and you will surely be able to hold long notes and tones! *
You got this! :)