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Yes, the original resistor was much bigger than a 1/2W unit. Your replacement likely burned up for this reason alone. A 5W metal film or wirewound unit would be a good replacement. As far as the 330 vs 350 ohm issue, I would tend to go with the value actually installed, rather than the parts list, assuming that the old unit looked original, and not a replacement from long ago.
The original resistor might have failed from testing a shorted tube (always run the shorts/gas test before testing emission or transconductance), or it may have been underrated from the outset. A 5W replacement would address this.
As the failed resistor is in series, I would check the 10K pot for damage, as well. It should exhibit a smooth change in resistance over its travel, with no open spots or abrupt jumps.
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