In order to dunk the ball cleanly in the hoop, your hand have to be at least 4 inches above the rim.
If you said you're still 5 inches away from touching the rim then you still have a long way to go.
You need to start by working on your legs and core strength.
My ways to improve vertical without all the weight lifting are:
Bike ride every day for at least 1 hour a day to improve your legs strength
Run or jog 15-20 minutes.
Toe raise for 20 minutes everyday until your calves get sore
Jump, jump and jump. The more you try to jump, the more your body and memory muscle will get use to it.
Also try jumping on a bench with two foot and then jump backward with one foot. Switch from left to right foot. Keep doing this and repeat until your legs get tire
Trust me you will see an huge improvement in your vertical after 1 months of doing all that everyday.
After your vertical is improve. Start looking for plyometric and other ways to improve vertical
It feel good to do a tomahawk slam in a random pick up game when nobody expect that you can dunk
