First, yes. It's based on Knight level. My character never used more than 4 a day, but maybe you'll find more use for them. As for multiclassing, don't ignore paladin spellcasting. With Spell Compendium for spells and Complete Champion for Battle Blessing (cast Pal standard action spells as swift), you've got some really good options. My favorite SpC spells are Rhino's Rush -- swift, your charge attack does x2 damage-- and Find the Gap -- standard, for round/level, your first attack goes against touch AC. For feats, did you mean for you or the Cleric? And if doing Knight at all (and little Paladin), may want to keep the ubermount, depending on what you want.
Let's see...Combat Reflexes, Leadership, [Power Attack, Improved Buckler Defense, Leap Attack] (if using two-handed weapon for damage dealing), Stand Still, Combat Expertise, Improved Trip are all good. Shield Specialization/Ward is helpful. Spirited Charge is amazing if going mounted, just beware of your mount not being able to go in tight spaces. For your mount in this case, Races of Stone has some feats that could help.
Really, though, if you're willing to abandon that variant paladin so readily, I'd advise checking out Crusader. It may be just what you want. Lets you control the area around you (even better than a Knight), survive tremendous assaults, protect allies from would-be hits (shield block maneuver), give an ally a free turn (white raven tactics), and heal people by making melee attacks (several maneuvers for this), and more. If you want to stick with Knight/Pal, level 3 is the best cutoff. I guess it's game-dependent, but I remember my last character with Aura of Courage, two dungeons in a row he had some good laughs as his best friend kept getting frightened and running away.
