Yes, but some parts of the CA had economic value, like a fertile part of Bukhara (cotton) and Kashgar.
Yes, but they’re secondary, you’re far better off growing cereal with farmers loyal to the state than growing cash crops in regions with potential rebels. The real value of conquering Central Asia has always been it enable to enforce stability, it was in the same way with the European conquest of a North Africa, the land itself was not important, the fact that it got rid of piracy was the important factor.
Another aspect have you thought about immigration to Russia, in OTL West European settlers was a important factor in develop these regions. In OTL the settlers mainly came from Hesse because this region allowed emigration, but with royal power strengthen in Mecklenburg the local duke could free the local peasantry and allow surplus population to emigrate to weaken the nobility and Mecklenburg is placed perfect for emigration to Russia (which usually was through St. Petersburg to the Volga and down along it).