Been singing ang gigging for years and stay booked however, still have issues such as, having to inhale lots of air to maintain my tone. Why? Examples of my singing can be found here: https://www.facebook.com/profile.php?id=100063557642120&mibextid=ZbWKwL
Requiring a lot of air to produce notes is indicative of your glottis (the gap between the vocal cords) not closing properly, leaving a gap of air. This causes a ”breathy“ sound and looses lots of air.
You may try to improve this by closing your glottis (so no air comes through), building up subglottal pressure and and performing a glottal stop. This may help you find a less open glottal disposition.
Like with anything voice related it is always helpful to get a trained teacher/coach to diagnose problems and avoid damage.