Nice nice job. I especially like the roosting tree in the run. Your chickies will be very very happy.
If you are concerned about using motor oil on your nest box, try mixing boiled linseed oil with mineral spirits, 50/50. Both can be found in the paint section of your hardware store for under $10. Paint it on with a brush, let it sit for 15 minutes and wipe down the excess. On fresh wood, there should be very little excess. This will give it a nice stained look, a waterproof finish and moisturize the wood all at once. Linseed oil is my friend. I haven't used motor oil, but if you're worried about it, try the linseed oil. I've been using it for 12 years (every spring) on my teak patio furniture and it still looks like new. I used it on my coop this spring as well as the waterproofing stain peeled immediately following our winter season.... aaaarrrrrgh!
I grew up in Coeur d' Alene and my Dad farmed in his childhood in Emmett. Idaho holds a special place in my heart.