When a Lord is dispossesed of his lands and titles, what happens to his soldiers and knights? Do they pass on to their new Lord? Are they stripped from their weapons and thrown out?

Well, it depends on the nature of their service. If they’re vassal knights and associated soldiery, then their service is bound to their tenancy of a given piece of land, so they’d stay.

If they’re household knights/sworn swords, they don’t have the security of feudal tenure – they’re wage laborers, albeit of a rarefied kind. So they might be kept on by the new lord, or they might be out of a job. However, they wouldn’t lose their weapons – those are their tools and belong to them, the same as a castle blacksmith and his tools.