What are the best home-care methods for dealing with tmj pain/soreness? can symptoms be brought on or aggravated by poor posture or sleeping position?

Yes: The TMJ can be directly affected by posture and the position you sleep in. TMJ disorders may be due to a number of different causes with different treatment modalities. The wrong treatment could do more harm. Without more definitive information regarding your symptoms, a non-chew diet, moist heat, and an OTC anti-inflammatory med might help until you can be properly evaluated.