Interesting situation. Possible to avoid cap-gains tax on rental?

[Jj Horst]

So my wife and I owned and lived in a duplex here in Austin TX from 2015-2017 (just over 2 years). We then moved to a new duplex and rented out the original one. We are now selling the original duplex in order to fund the purchase of a single family home/primary residence. 
Its been too much time to claim we lived in the for sale duplex for 2 of the last 5 years (its been 7) to avoid cap gains. I was curious about 1031 exchange but it sounds like selling a rental for a primary residence would not count as "like kind" properties. 

I'm not trying to break any rules, but obviously if I can avoid paying taxes I'd rather do that!

If we sold the duplex, and then bought the single family home. But stayed in our current duplex, would that open us up to be able to claim 1031 exchange exceptions? How long would we have to NOT move into the single family home for it to qualify? Would it need to be leased at some point?

Obviously it sounds like I need to talk to a real estate tax professional, but I thought I'd get the communities opinion before going down that round.

(We don't want to sell the duplex we're living in now because its much larger than the other and will bring in almost double the rent)

Thanks!