Also, how is the current scarcity artificial? Are we limiting the output somehow? Could we for example produce much more cheap food, but we don't, in order to keep the proles scared?

He is saying that we limit his inputs. He wants to, for example, be able to produce his own food as to not have to rely on deals made with other people to acquire food, but notes that society carefully controls who has power over the land that is able to support that production, leaving nowhere for him to do so, and leaving him at the mercy of being able to reach agreements with others – others who may not want to make an agreement with him – in order to eat.

He says that without a strong society he could push anyone standing in his way of the land aside (by brutal force, if necessary), but an entire society standing in his way is a force too great. As such, he believes that great force should provide suitable compensation for the restrictions it imposes (e.g. if you aren't permitted access to land to produce your own food, you should be guaranteed access to food by some other means).

You don't have to obey them now either, but don't come crying to us when someone kills you for trying to take it just like they would have if you tried to come in and take over some tribe's land in the past.

The only difference now is that you might get the luxury of just going to court or jail.