Re: S2 7.9
Cannot help on the inboard/outboard weight distribution issue - for info on that I would go to the class association web site.
And . . .
"should I be concerned about spiderweb cracking like this in the deck?"
Well, yes. My 7.9 had water intrusion in that whole area - from that turning block, to the genoa track, to the winch and down to the stanchion - on both sides of the boat. There are ways to check. Look from down inside the boat. Are there signs of water coming in? Press down pretty hard with your finger around the cracks from the top. Does it compress? If it does, you've got bad core. Use a moisture meter, and get a survey. Also check carefully around the mast step. Mine had water there too.
That being noted, it should not necessarily be a deal breaker. I did the repairs myself. If you hire it done, it will be expensive.
I'd also note that the boat was sailable with those defects. I kept sailing and waited for winter & indoor storage to do the work on it.