Well, I think that "phrasing" and "playing dynamics" are probably 2 different things. Phrasing is developed over time; it really can be described as "your voice" (and I don't mean how you sing ). As you gain experience and knowledge, you'll incorporate them with your creativity and your phrasing will reflect this. Listen to some good horn players; their phrasing techniques are adaptable to guitar playing and should open new horizons for you. And don't forget that rests (i.e. silence) are also a part of effective phrasing.
Playing dynamics, on the other hand, I would describe as how the guitarist(s) plays off the other musicians in the group. The lineup of the band mostly determines this. For example, in a 3 piece group (guitar, bass, drums) the guitarist has to fill the space not occupied by drums / bass in the rhythym parts ( whether it be chords, chord fragments, double stops, riffs etc.), and when/if he solos he better be on the money (there's no place to hide) and the rhythym section has to be tight. My current band is essentially this, though our female singer does add some keyboard work on some tunes.
In a 4 piece group (d/b/g/g/), the 2 guitar players need to live in their own space and not trample on the other guy (easier said than done). Whether it be lead/rhytym (e.g. Beatles, Dead) or lead/lead (Allman Bros) this interaction is critical to sonic excellence. I've been in both of these situations ( lead/lead and I was lead to a rhythym player) - essentially the same but different. Two guitars playing the same thing for the most part becomes just noise IMHO.
As more musicians are added to the mix (piano, organ, harp, slide etc.) the dynamics of all these parts fitting together becomes more complex.
So, the next step for you would seem to be to start playing in a full band situation. This is the only way you can work on your "playing dynamics". And by all means get out there playing in front of people. Nothing is more satisfying than nailing a song (or songs) with an appreciative crowd on hand. EXPERIENCE - there ain't nothing like it, but it comes with time. You're young yet - you'll get there with a little patience.