The point of c2 is to give a high frequency boost, since it's a small value cathode bypass. V2 current measurement will be seriously off if cap is shorted, if open you will simply lack the high boost.
C6 value being extra large should be okay. On power up, I would have the unit in bypass, and check c6/r13 junction for presence of DC. I'd check it initially, and if it seems okay, again after 20-30 minutes to be sure leakage hasn't increased. If it were me, I'd tie off the original leads somewhere and put in a new cap. Probably choose a 0.33/400. You ABSOLUTELY can't afford leakage possibly taking out the next transformer.
C7, I'd tie off the old and put in a new, again 0.33/400. You can't afford leakage possibly taking out the next transformer.
C8 measures too high, and can potentially let too low a frequency affect the side chain, which can lead to pumping issues. The other schematic shows it as 0.1 mfd. For the same reason, you also shouldn't enlarge the value of c5 beyond 22 mfd.
C1, c3, and c? (c3 companion) can all be made 100 mfd to improve low frequency linearity.
new c9 with accurate value (0.22 okay; you will probably not ever keep it near 10M r24 value) may also improve limiting consistency.
The 6mfd cans are 99% likely to be fine. Just be sure none are shorted or have measurable resistance under say, 1M. You really shouldn't see a value even that low, but you may, being in circuit.