Polyjuice and Snape

[B.G.]

No: HPFGUIDX 133797

BG writes:

Why is there a vat of PP in the school this year?  Who is using it?  
DD and Snape?  Is Snape dead and DD went off with Draco?  I know it 
sounds bizarre but after reading JKR's interview on Mugglenet.com I 
really doubt that DD is dead and I was so sure before.  Maybe they 
got the idea from Crouch,Jr. who infiltrated Hogwarts as Moody using 
the PP.  I believe the blast at the top of the tower is the 
Unbreakable Vow being broken by Snape (as DD).  DD(as Snape)cast the 
AK knowing that he didn't mean it and therefore it wouldn't work but 
the broken vow killed him.  The body was completely wrapped at the 
funeral.  If Snape (as DD) had returned to Snape no one would have 
seen him.  The flames enclosed him in the tomb and no one can view 
the body - ever.  

Why did DD let Snape have the DADA position when he knew it was 
cursed and that it would be Snape's last year?  DD and Snape knew 
that he would not keep the UV and gave him his last wish - to be the 
DADA's teacher.

The portrait confuses the issue but maybe that was pre-arranged too - 
we'll have to see if DD's portrait acts the same as the other 
previous Headmaster's portraits.

It all fits, not neatly, but fits.  Thoughts?  Am I way off base?