Has your water supply changed at all. I believe that carbonation and head retention can be adversely affected by PH level and water chemistry. There are articles out there that explain this in greater detail. You may want to have your water tested or at least consider this as an issue.
I think that screen sticking up was part of the problem also. I know you mentioned it above, but you really need to make sure that remains at the bottom of the mash. Good luck on your next brew.
Monster mill MM2, awesome mill. You can control the crush by adjusting the gap between the rollers. The mill is solid and will increase your efficiency by at least 5-10 percent, maybe more.
I am out of town. Can you PM me and I'll try to P/U On Sunday when I get home. I can Bring cash or paypal you before I come. I really appreciate you doing this for us home brewers.