If you feel the 50 is comfortable, stick with it. Seems like you've got it dialed in. If it's going to bug you forever, get the 52. You'll be able to dial that in as well. It sounds like you are in the middle of the two and could go either way with stem and seat adjustments. Also, your handlebars look like they are at an odd angle. Do you want the drops on that bar parallel to the ground like you have them or do you want the top parallel to the ground and drops at an angle so they are perpendicular to your arms. That might keep you from hitting your knees on the bars.