hey there @Nokturne!

like you, playing by ear comes more naturally to me than playing by sight....

but, over the years and with much practice, I've been able to get to a point where I feel fairly comfortable.  so here are some of the steps I took/take....

1.  I know it can be boring and not everyone will agree with me, but learning your scales is HUGE!!  so....  for example since the lowest note you will play on the violin is a 'G', I would find a printout of 'G major' scale (treble clef, remember) that spans 2 octaves.  Then, I would map out where those notes fall in 1st position according to your violin finger chart (you may already know your fingerings fairly well, but thought I should include this step anyway).  then, PRACTICE moving up and down the scale as you watch the notes on the sheet so you become comfortable with where the notes fall in that key.

2.  learning to read music is as much about how it progresses as what the notes look like.  take a look at some different pieces of sheet music and start to look at the patterns the notes make.  FOR EXAMPLE.... they start low on the staff and climb from line to space then return in steps back down (ie. GABC DCBA GABC DCBA), or they move from a lower note to a higher note repeatedly (ie. GD GD GD GD) or, they climb for 3 on lines only and then repeat the pattern (ie. GBD GBD GBD GBD).  once you start noticing different patterns in the piece, start trying to play just the patterns you find (repeat each one quite a few times) so that you can start to associate what each pattern looks like to how it sounds.

3.  learn what 'intervals' look like.  the term 'interval' is used to describe the distance between notes and gives that distance a numeric name....  if that makes sense.  for example (and you may want to find or draw a staff to follow along with this explanation), if the first note in the piece is a 'G' (second line from the bottom on the treble clef) and the next note you see is a 'B' (third line), you would count the 'G' line as 1 or 'first', the space above it as 'second' and then your 'B' (on the next line) would land on the 'third'.  SO, going from that 'G' to the 'B' above would be an interval of a 'third above'.  likewise, you would do the same for each set of 2 notes learning what each interval is named and what that looks like....  for example, start on a LINE and moving up to the next SPACE would be a 'second above', starting on a LINE and skipping both the next SPACE and LINE and moving up to the next SPACE would be a 'fourth above', and the first note on the third LINE of the staff ('B') skipping the LINE below and moving to the next LINE below ('D') would be a 'fifth below'.  play these once you begin to recognise the intervals by sight and you will notice how they sound and feel.  some people relate the first two notes of a tune to remember how each different interval sounds

second above.... "Doh a deer, a female deer" 

third above.... "Oh when the Saints go marching in"

third below.... "Swing low, sweet chariot"

fourth above.... "Should auld acquaintance be forgot"

fourth below.... "I've been workin on the railroad"

fifth above.... "Twinkle, twinkle"

sixth above.... "my bonnie lies over the ocean"

.....well, you get what I mean!  you can figure out more if you find this helps.

4.  Rhythm.  find some resources that help you learn the value (how many beats or counts) each note gets in a measure of music.  use some sheet music you have around (and aren't familiar with) and start going through them in 4 or 8 bar sections.  sometimes clapping or tapping the notes/rhythms out works better than trying to play with the notes at first as that way you can just focus on the rhythms without getting caught up on whether or not you are playing the correct notes.

5. learn to play in different keys.  in step 1, you started with a 'G major' scale.  learn some different key signatures (remember with those, they note the sharps or flats you will use at the beginning of the piece only.  throughout the rest of the piece, for the most part, you will stick to using those every time you play the corresponding notes throughout the piece -unless it is changed by a natural sign).  try moving up to an 'A major' or 'D major' scale next as those aren't too difficult to play on violin (for now, i'd recommend sticking with the major scales/keys).  *remember to try to move up and down 2 octaves if you can so you get more familiar with what the notes look like on the entire staff.  also remember you will have different sharps or flats to think about in each key, which is why sometimes it is a good idea to focus on playing in one key until you are quite familiar with it before moving on to another.  you have a good ear, so it will probably tell you if you miss one of those sharps or flats.

anyway....  my response was ridiculously long, and won't answer all your questions, but it's a good place to start anyway!  good luck!