Hi! I'm glad you're enjoying it!
On crops; the intent is that when you farm, you plant a field full of one crop type. So it's not just one turnip, it's one field of turnips. You can allow yourself to plant multiple different crops in the same field if you want, but you only progress one of them when you take the Farm activity, so it's not really helpful to have more than one.
On Trivial objects; a Trivial object costs 1/5 as much as a Minor object, so you can build five of them out of enough of a material to make a Minor object.