You don't need Horse Archery for crossbows. Also save that 1 Shield point and go for Shield 5 with Plate Covered Round Shield that has very similar stats to Steel shield. This way you can convert those spare points and go for 18 strength and additional PS. As for the light crossbow you won't get many kills with it; it acts primarily as a backup weapon. Use it to scare horse archers (they are usually riding very cheap horses so it only takes very few hits) and infantry with no shields.
As for equipment Shield + Sword + Light Crossbow will leave space for only 12 bolts so use them wisely. I usually only fire at enemies right next to me.
Instead of wasting points on crossbow invest them in 1h since this is where most of your kills will come from. Personally I prefer to spend them all on 1h for this reason, look for WaltF4's post: (
http://forum.c-rpg.net/index.php/topic,1357.75.html). (Investing in crossbow wpf is just not worth it, especially if you only fire 12 bolts per round) .
Also remember this build only works if you are driving a charger or plated charger. Anything weaker will go down in seconds so you might as well be traveling on foot. A large treasury full of gold is welcome to pay for repairs, plated charger alone costs about 3200 in repairs not mentioning armor.
I suggest going for Horse Archer build if you want to get many kills with a ranged weapon from a horse.