Help me design my kitchen (see pictures)

Use a grease filter like this under your fan. I would vent the exhaust hood right away. An operating hood cuts down on the cleanup and odors quite a bit. Also, I made metal backsplashes to contain any cooking spillage. I don't regret that at all.

I like what you're building here. A van is challenging because of the space requirements but it seems like you are able to locate everything essential. Looking forward to the next installment.