It's 2 bed/1 bath each, and it's on a 10,000+ square foot lot with parking for 4 cars (two garage, two additional off-street). 

There is an unpermitted addition (600 sq ft) that I can try to permit for about $115 a square foot over my original appraisal, or about $70k.

The best chance of this working is to have a large amount of foot traffic already in the area. 

Now that I am a Realtor in Colorado, I am also required to disclose that on my listings as well that I have an ownership stake in a property in the advertisements.I also have not really seen a difference with the tenant's treatment of me as the property manager vs being the owner except one time a tenant did try to pressure me into paying for a silly upgrade saying that as the owner and I could afford it and the $100 month rent increase should pay for the new ceiling [The upgrade was to re-texture the whole ceiling of a 1000 sq foot apartment because it had swirls and minor hairline cracks (built in 1920) and this tenant did not like the swirls -- changing the swirls would cost thousands and not result in any more rent]

Mostly hardwood (oak and maple, some hickory some beech) I would guess but not a lot of big stuff, I would say the biggest trees are probably about 2 feet in diameter with maybe a few 3 foot trees in there.

Well, I’m basing this ARV on the average sold price per sq foot for the Englewood zip code.

Today from 30,000 foot level is bad timing. 

I have no clue.However, I have also been keeping track of the average price per square foot of houses being sold in those same zip codes. 

Kind of sounds like you two got off on the wrong foot.

The average price here is 151 per square foot. its a class C+ neighbor.