You could always save up 20% and get a traditional mortgage, or save up 5% down conventional loan and buy your property to live in for a year, then convert to a rental after 12 months (least risk), then repeat.

While natural gas is perhaps "cleaner" burning than other tradition fuels used for electricity generation and heating, anything that you burn, produces greenhouse gases.   

Question: did you purchase the property through a traditional loan?

Do I want to buy the house for more that $450,000 (if I'm given the choice) so that when I sell it and there's a gain I won't get nailed in taxes? 

Banks and traditional lenders will likely balk, but there are alternative lenders who will look past your BK.  

If they are down to drop PMI without refinancing, and you are given the choice between paying for a cheap BPO or drive by appraisal, and a more expensive full appraisal, to confirm your equity position, pay for the full actual appraisal.

We can still fund a deal with this type of structure although the funding fee increases, That is why #1 and #2 are preferable choices.

Where FHA deals can be more difficult, I am having trouble understanding how that alone is preventing your offers from being accepted and, where inventory is very low right now, suspect the $100k approval is what is limiting your choices most of all. 

I've always thought seller financing was a good option in place of traditional bank loans but I'm not really seeing a benefit after looking into it.

Ask them if they do any real estate investing themselves or if they have experience on creative/non-traditional financing.