Sump and Skimmer questions

Ok. Please try to bear with me, this is going to be long...
I am in the planning stages of a new reef setup and I'm trying to get
a handle on some plumbing concerns. Before I ask a potentially dumb
question, here is my plan thus far:

75 Gal. AGA with their new "MEGAflow" overflow rated at 600 GPH.
Old 45 Gal. AGA to be used as sump/refuge.
Considering Red sea's Berlin classic in sump skimmer with RIO 2500

I've done considerable research but my head is spinning with all the
possibilites.

My questions:

1. Considering I will have approx. 5' of head for the return, and to
not exceed the 600 GPH overflow rating, it looks like I will use a Mag
7 as a return (rated at 420 gph). The Rio 2500 is rated at 748 gph.
Does this configuration pose a problem since the skimmer will have a
higher flow rate than my return?

2. The sump will be partitioned into 3 sections; overflow from tank
area, refuge area, and return area. Into which partition should the
skimmer be placed? before or after the refuge? and how much space
should I plan for the placement of the skimmer? will the output of the
skimmer just dump back into the same partition?

3. As far as baffles are concerned, where will I need them? Before
refuge, after refuge or both?

Thanks for any help you might offer and I apologize for the length of
this post.

-Scott