Couple of quick thoughts.

Did you include the weight of the shield - 10-20lb - in with the armour?

Also, you've gone a bit light with the weapons, I think. The primary melee weapon, the sword, varied between 2.5lb for a light one to 4.5 for a hand-and-a-half sword. Swords were, however, prone to break and not always effective against other armoured knights, so a second weapon would be carried, usually an axe or mace, weighing between 2.5 and 3.5lb, or a warhammer, which was nearer the 4-5lb range.

But the knights' main weapon was his lance or spear. In early times this was simply a stabbing spear, 5-6 feet long with an iron point, that was used in ordinary melee combat against both cavalry and infantry and probably weighed in at around 5-7lb. By the high Middle Ages, however, the lance was a one-use weapon, designed to be used in a massed charge agaisnt other knights. They were some eight or nine feet long, with a metal vamplate to protect the hand, and a barbed steel point. The idea was to used the momentum of your charge to shove the point into an opponent, then break the shaft (hopefully leaving the point embedded), then either retreat and get another lance, or drop the butt and go to your melee weapon. They would probably weigh around 10lb, if not more.

So, by my calculations (and ignoring the misericord), a high Middle Ages weapon loadout would weigh between 15-20lb.

Not sure how much difference that would make, as in general I agree with you.