#1
So i was wondering if you are supposed to use all of your fingers while finger picking. Im in a really bad habit of just using my thumb, index, and middle finger. If anyone has any suggestions of exercises or songs to practice to incorporate my ring finger or even the pinky that would be great.
#2
I almost never use my pinky, some flamenco players use their pinky but it's still very rare. For practicing, just fret some chords, and play the root note with your thumb and the upper three notes with your index, middle and ring finger. Like this:

E|----------0---------------
B|-------1----1--------------
G|----2----------2------------
D|----------------------------
A|--0---------------0-------
E|---------------------------

Just switch chords. This way you can train your right hand and left hand at the same time. Except when you're very new at this, just play open strings and focus on the right hand. Make it more difficult for yourself as you progress.
#3
i got out of the habit of just using the thumb,index, n middle finger but pretty much fretting major chords and plucking them with all my fingers (not simultaneously). at first it felt awkward especially with my pinky but after awhile its fine, and sounds cool.
#4
fingerpicking is a series of patterns, that's all. So the best thing to do to incorporate your ring finger is to start using it.

A good song is slightly stoopid's collie man which uses a pattern of thumb, then the three fingers per chord.

-2--2--2
--2--2--
---0--0-
--------
--------
3------

then go to Am, hit the bass string with the thumb, then "roll" the next 7 notes on the top three strings. Then go to an F chord barred at 1 and do the same pattern with thumb on lowE. then finish with a strum of the C chord. Then repeat.

Or just start scales with TPMR and change it up to TMPR or TRMP or TRPM etc, until they are all fluid. This is going to get your hand in shape faster than playing any song because it is repetitive and relentless. Get a squeeze ball from a rock climbing store like REI or Dick' Sports and squeeze it between your Ring finger and palm using only your ring finger and relaxing the others as best as you can.

The only way to get good is to train for 10,000 hours. There is no shortcut.