Note that the Audioregenesis PC-10A board was not created due to issues with the original design, rather the difficulty and expense involved with obtaining good NOS or used 7199's. The goal of the PC-10A was to create a board that did not degrade the performance, while being able to use much less expensive, and plentiful, 6GH8 or 6U8 tubes. While more stable than the Sovtek 7199 (in the SCA-35 application), there were some examples among the many tubes tested during development that did display some stability problems. An additional R/C phase shift network was added, along with the 10K resistor you mentioned, to ensure the circuit would be stable with all 6GH8 and 6U8 type tubes. I tested many, many different tubes. It is important to note that the these additional modifications are applicable specifically to the 6GH8 and 6U8 tubes, and I would not be surprised that they have little or no affect in your case. In fact, it is even possible they could degrade the performance with the Sovtek tubes.
As to the 27K resistor in the phase splitter, effective "impedance" would be the more correct term to use when describing the result of the parallel combination of components. You would not be able to measure that with an ohmmeter. As far as the actual audio signal is concerned, the 1uF capacitor can be considered a short circuit, and thus the 22K result.
Now, as to the positive feedback, in the case of the SCA-35, Dynaco had to squeeze all the gain they could from the PC-10 to make up for the loss of the passive tone controls which directly precede it, since there is no preamp associated with the high level inputs, only the low level inputs (PC-11). The gain is required to achieve typical expected input sensitivity for the high level inputs. It was a careful balancing act to achieve the required gain while maintaining stability as well as low distortion, all achieved with circuitry specifically designed around the (real) 7199. Amazing they pulled it off so well.
I should also mention that the 7199 was intended for high quality audio applications and originally exhibited a suitably low noise floor. It is my understanding that as production of these tubes was nearing it's end there were some occasional issues with quality, higher noise being one of them.
With the Sovtek tubes, and the 1uF cap. to ground, you will likely not have stability issues, and it could well be that you personally prefer the sound of the Sovtek's. And really, that's the most important thing. It has to sound good to YOU.