I agree if you have the oil out, i'd be inclined to remove drop box and side cover with the pump attached you'd get a good view of what is occurring, if your lucky the steering pump hasn't worn due to the dirt in the filters. Check the charge pump filter screen along with drive gear, not good news if you need a new charge pump as it is quite a challenge to swap. The steering pump controls transmission pressure as well as steering. Hence your problems. When the pump is worn you can bring it back to life by slackening pressure outlet on pump and cranking engine, till oil runs out air free. Then tighten fitting and away you go.