Speed accuracy- how accurate is accurate?

It is all about enjoyment. Wow / flutter is more important in my mind than absolute pitch. 

Question is, how much effort are you willing to put in and whether it will be worth it. :-)

The table is rock steady- how much effort am I will to put in? Considering everything sounds right, not much 

There is your answer. :) But mathematically, it is off by 0.6% of perfect. That's pretty good. 

By most accounts, the iPhone method is not the most accurate way to measure platter speed, but it puts you in the ballpark. So I would not conclude that the speed error of your turntable amounts to the difference between what you measured and 33.33 RPM. It might be more, or it might be less.

"Running an iphone...33.55"

I trust my ears over an iphone. Other than a constant,real time,calibrated Phoenix type controller contraption, all those "apps" are going to vary.

Even then, neurosis continues.

Try playing a recording with music in standard A440 tuning. Possibly every  album will be different plucking a guitar or playing the note on a piano as reference.