Numbers for long swords on horseback:
For mounted use true one-handers always win, mostly with speed though, because raw damage isn't all that important. Bastards are a compromise, which allow you to train and be truly effective once dismounted.
Remember the only differece between a 'bastard sword' and a true two-hander is you can actually use a shield,
I almost never do that. I use bastards, because they are faster and more effective at face-hugging distances, hence better for crowd-control.
you receive the 2h -35% penalty on both. No time on hoseback is a bastard better, no way - no how - no when.
True two-handers don't work very well on horseback at all, and on foot I'd also prefer a bastard most of the time. Extra reach doesn't buy you much, as you've correctly noted already. True one-handers are better on horseback, sure, but they won't cut you out of the crowd once dismounted as effectively as a bastard without a shield, and sometimes even with it.
(Besides, I'm not sure about the damage penalty. Bastards "seem" to hit harder in one hand than true two-handers, so I don't exclude a possibility, that we do not understand fully how the game calculates damage. Speed factors quite a lot into it, doesn't it?)
As for blocking in melee, if you have a fast weapon there is no need to use your shield, shileds are mainly of benefit against missles in Warband. Though, if you have a slower melee weapon and a faster shield sometimes shield blocking helps.
You can't block in two different directions, and AI is able to attack from all of them, because they merge into each other. Hence when mobbed I tend to circle and spam fast attacks. With decent proficiency it seems to work better than trying to fight with a shield. They don't last all that long while constantly punded by an angry mob...
As for a lance early, not if you want to be an archer. To be a horse archer takes a lot of investment. You need to build HA, PD and riding as high as you can. You also need to stick all your weapons points in archery until you can't anymore.
Lance doesn't require any points into it to be deadly. Archery grows fast with my style of play anyway, and this time around I didn't even pump it all that much. Above 200 I don't see much difference anyway (finished at way over 400), and you'll get there quite fast without major sacrifices. So I pumped crossbows and throwing, to make tournaments less frustrating and have more fun.
Horse archer is probally the hardest type to train and you had best dedicate yourself to it early or you will never get there.
I always played horse archers, with one exception, when I decided to try melee build (crossbow for sieges). It was boring and I didn't finish the game.
Anyway, it's not as hard as you make it sound. All it takes to pump up archery is to get a fast horse, circle the crowd counter-clockwise at full gallop and shoot until your run out of arrows. Some of the shots are bound to hit someone, and the game thinks it's extremely difficult, so it gives you a lot of points.
Works perfectly against bandits in the early game. You go first, at an angle on their left. Once you hit some, they turn to face you. Works especially well if you get behind them, so that your cavalry can hit their exposed backs.