I'm pretty much in line with your thinking. Priority #1 was stop the killing of ethnic Russians in the Donbas.

#2 was get the water flow to Crimea secured. Why noone talks about this super-obvious point is a wonder to me.

#3 (maybe 2.5) was a landbridge between Crimea and Donbas.

The rest is gravy:

#4 block/take Odesa and create a land-locked Ukraine

#5 create a landbrige to Transnistria

#6 take Kharkov? Sumy?

#7 fill in whatever is possible of the crescent created by 3 +6 above.

At that point Russia would have control of the entire east and all ports. A great negotiating position.