Yes I would continue to drive the Auto-Rx to 3000 to 3500 miles, if the oil is still light and honey colored. I would expect the varnish or discoloring in the valve train to resemble the progress on the dipstick, which you have noticed. Get all your money’s worth of cleaning with your Auto-Rx purchase.
I think that the Rotella T6 is a very good oil choice moving forward, especially with the maintenance dose installed with it. I do question the weight/viscosity choice however. I would think that a 5W40 Rotella T6, would give you the best overall performance in your older car. The 5 weight will produce less parasitic drag on the motor and will pump easier on cold starts. Whereby indexed to a viscosity of 40 will maintain a fairly robust oil film thickness for likely some worn parts internally.
I am a bit puzzled by your comments that the valve train is now noisy. Normally that should quiet down. Do you have a ticking sound? A ticking sound can be a whole host of issues. From an oiling perspective, a hydraulic lifter that has trouble building pressure can cause a tick, sometimes referred to a sticky lifter. Auto-Rx will clean up deposits on the lifter as well as the valve guides. A tick can also be the sound of a failing fuel injector. Or even perhaps a slight exhaust manifold leak.
If the motor is not producing a plume of blue smoke during cold morning starts, then that is an indication that your valve stem seals and guides are in good shape, with good valve sealing. With 200K on the odometer and no oil consumption issues, the motor would seem to be in good condition.
