Hi Kscorder
Sorry to hear you have such lingering pain in your shoulder.
A couple of questions - does the shoulder movement/crunchin correlate with the pain you feel around your shoulder blade? Does one noticeably bring on the other?
There is a good chance it may be postural as you say but another area worth looking into is referral from you neck.
This is pretty difficult to figure out online so it would be worth booking in with a physical therapist or equivalent profession over there to check this side of things out.. especially if gradually worsening. In the mean time try improving your posture for short periods of time and set reminders on your phone/screen in front of you to 'reset' every now and then. If the pain decreases with this change then you know you are on the right path.
Hope this helps
D