I'm not worried about the switch to synthetic at all at this point. I've driven it a couple of days now and the oil is clear as new.
I don't think I'll be disabling the power steering though. When I EOC around a corner, it requires significant effort to turn. I doubt a hose reroute would fix that adequately. (I have done it before on a race car and it does help some, but not enough with lower ratio racks.) I think the only reason it is such a non-issue with the Tercel is because the car is designed for some serious low speed off-roading which is what it's there for.
As for the tires, I don't wanna say what the sidewall marking is. I'll just suggest that sidewall pressure ratings are based on maximum loading of the tire under stress, and my car is about 75% of their maximum load and I don't intend to be running any autocrosses with them. Regardless, it's going to be a moot issue very soon, as I have the Sumitomo HTR T4s on order and should have them on before next week.
Yipee! No more fear of blowout from overinflation. We'll see how well the T4s hold up now. One intersting point is that I was told Sumitomo does not offer a warranty on these tires. Perhaps they understand the mindset of some of us who install them.
And yes, 51 psi is the maximium pressure stamped on the sidewall.