There should be a sandbox mode of the game, where you can have all of the tools and be free to make whatever you want. You should also be able to save designs and share them in the sandbox mode.
Someone in your caravan is walking at 5kmh, so everyone/thing goes at 5kmh. If you bought something that goes at 3kmh, it would bring the speed down to 3kmh for the entire caravan.
Zombies are both smart and dumb. I completely closed off an area on all 4 sides and diagonally. When I came back later, there were more zombies. They're smart enough to build tunnels, but not smart enough to build them where it counts. A couple weeks later and that area's overrun.
A crate has 200 million cups of tea. If google's right and tea costs 1-3 dollars per cup, then that's 200-600 million dollars for one crate. Crates normally cost 10-30 silver (for simplicity), so 1 silver represents 20 million dollars of our current money. If you retire on 10000 silver, you're richer than Bill Gates (much richer). Unless tea has become much more expensive compared to the cost of living, you'll have 200,000,000 dollars. If you think 30-90 silver is a more accurate value for tea, then you'll still be rich enough to live in a house made of solid gold.