Complicated problem hummm...
You are right I don't see the bipolar cap either in the schematic and belive me that was the more likely candidate. Well in this case. I would double check:
1-Q303 (Replace it even if it appears to read good)
2-D303, D304. (Pincushion Diodes I was telling you). Replace them even if they appear to read good.
3-L303
4-C115, C116, C326. Meassure them with your Fluke in Cap mode. More than 20% deviation and they affect pincushion and width; but eventhough you should still be able to adjust H-size.
5- I don't belive you have a CRT Chassis missmatch. Eventhough you could be able to adjust H-size, even if it is too wide.
6- Use a Scope and meassure the waveform at pin 7 IC 302. Take a pic of the waveform and post it here. I want to see if it looks good or not.
I had exactly the same problem with an NT-2702S and it was what's in this schematic Q303.
If you are willing to pay for shipping back and forth, I will take care of it for you for free just for the fun :-)
www.adrianelectronics.com