Jay Brown reported on March 22, 2016 that following the 15 million shares purchased in the first two months of this year non-GAAP book increased to $32.55. per share. He did not provide a GAAP book but my calculation is $28.05 which is spot-on with your estimate of "around $28.00."
I agree with all you have posted though we are currently above both the 50 and 200 day average. Today's trading was significant because we had a near double in volume in the last hour, from 2.8 million to 5.3 million, and yet the stock was fading and closed near the low of the session. This type of pattern often develops on option expiration Fridays when professional traders tap down the share price, particularly going into the close. So no surprise there.
Short interest at month-end February is 19 million, very high in my opinion given the sharp reduction in shares outstanding and recent share price gains.
Likely volume today 1.6 million. Trying factoring that into 22 million shares short. Stock possibly getting a little scarcer. The very manipulation that has occurred in these shares for months and months might now be coming back to fully encircle the bearish bettors. I have liked MBI for the values and fundamental story but would not hurt my feelings in the least if the shorts got ripped, pillaged .and tattooed