Trying to confuse me again? There's no G here? 
Do not try to hold the lower D, just let it go and play the rest. Remember, this is baroque, it can/should be detached. Better jump than stretch!
EDIT:
Since you seem to be working quite seriously with this already, did you teacher talk to you about accents? In this piece it is very important to play the first note in every measure more pronounced, otherwise it just does not sound right.
My teacher said this piece was above my level when he gave it to me. We've only looked at it once and only worked on the left hand movements then, he scraped of the lower d for simplicity's sake, but I'm a stubborn guy:p.
No, I'm not trying to confuse you, but on my sheet I have to have my left hand in the D position (thumb on the D), therefore my pinky will be on the G
1=D
2=C
3=B
4=A
5=G = Pinky
Now, I hit the D, so number 1, then I would want to hit the lower D (as shown on the sheet). That D is part of a beam though, a beam where the second, third and fourth note of the beam is CBA but not the CBA left from the lower D, but from the upper D.
So when I hit the lower D with my pinky I could go 2 ways:
Hit the C with my 1, B with my 2 and A with my 3. But according to the sheet I would need to hit the B again and be in the D position again. So that way would not work.
The other way is simply hitting the C with my 2 and move from there. See where the problem arises? I switch pinky lower d and hit the upper C with my 2 to get back in the D position. That's difficult for me now.
Edit:
Maybe I should just go with the first way and get back in the D position when I need to hit the D agian.