Breath is not about inhaling more
The trainable skill is stable release and support. If you inhale a lot but release air unevenly, the voice still wobbles.
Endings reveal breath control
Many singers start on pitch, then fall or fade in the final second. Watch endings closely instead of judging only the attack.
Stabilize before extending
If 4 seconds is stable, try 6. If one vowel is stable, add a phrase. Length should grow from stability.