Opus, yes I can put a day limit in PPD, good idea for people that have a high number of posting new members. I've been seeing weird stats in mine too. I'll put in a 1 day limit just so it won't show weird stats, but you will be able to change that in the script.
I'll squeeze the total messages in it too.
I don't have any server load statistics to tell you, but you can use
vBMicroStats to check yours out. This isn't the kind of page that is used often, so it having a higher use of queries should be fine.
(it's actually loading fast for the amount of stuff it does in my opinion)