Taking the load off the tabernacle pins seems to be a reasonable thing to do with few apparent downsides.
The stemhead fitting is another matter. Probably worth beefing up, but how to be sure your repair is strong? (Mine's a DS1 with a different kind of fitting.
About rig tension: having some slack in you leeward shroud is fine. Definitely by 8-10 knots. (I don't have mine set up aggressively for racing, and winds I sail in tend to be on the moderate end a lot, so I may not be taking things as far; still, weather helm is moderate until I'm overpowered (for given crew weight/degree of hiking).