1. For aircraft performance, use the DA. If the chart doesn't have a column close to your DA - interpolate (real temp ISA+13 = about halfway between the settings for ISA and ISA+30)
2. Depends somewhat on what it is that limits you to 17000 feet MOA. Pressurization (differential not sufficient? Or no pressurization, just nasal oxygen?) Structural (too high a pressure differential?) Engine? Equipment (insufficient for USA class A airspace? Not RVSM-compliant? etc.)
Or was 17000 just a number you picked as an example?
As Vessbot says, the definition of DA is "PA corrected for temperature" - so I'd take DA as your "effective PA" and stay below 17000 DA, unless I had clear evidence from the POH otherwise.