Maybe it would be nice if everyone had lips that align, but we're not clones. Such is the view from the side. No more pressure of the mouthpiece is needed beyond an air seal between your lips and the mouthpiece to play any note. Back off that left elbow pressure! Breath control is essential! It should improve with practice. Take a breath at every rest in the music, otherwise surmise phrasing and pencil mark it, catching a short breath between the phrases. The higher notes require more air pressure, but practice the lower notes, playing them long, whole notes tied together, two notes in the beginning, then 3, 4, 5 ad infinitum over time as your breath strengthens. Next, still with whole notes slur up a tone, 2 tones, 3 tones etc. Introduce sharps and flats as appropriate and build a chromatic scale of whole notes, half notes, quarter notes, eighth notes, sixteenths, and possibly 32nds. Ascend and descend this scale. What I've put forth is a practice regimen I personally have used and still often use. Excellence doesn't come quickly but if you are diligent and persist, it will come. As others will say, get a tutor ... one that helps you. I once had one who was also my instrumental music instructor in the lower grades and later my high school band director, but he tutored me often twice a week for an hour. I now relish those hours, as Dr. Cameron knew his stuff an could play rings round the rosy with his trumpet or cornet. Point, it helps a lot when your tutor is proficient on the instrument you play.