Can a reactor be operated at both reflux and above atmospheric pressure?
You could theoretically boil at the higher temperature but why would that be a requirement? Why would you require reflux specifically if you can actually heat the formic acid to higher temperatures under pressure? Heating should work on its own and degassing to drive the equilibrium should work with a back pressure regulator. However,  most lab glassware will not take that pressure. You normally need some stainless steel pressure equipment. 
One way might be to use plug flow reactors rather than bombs.