I agree that the PHL to EWR/BWI transfer is a hassle, but not a $550 per person (or more like $300 per person if you factor in extra legroom seat purchases both ways) hassle.
The PP website states that there are two PP lounges in LIS, though I haven't been to either so cannot comment on their quality. There are currently no PP lounges in EWR.
You should be able to book an open-jaw UA fare into LIS and out of OPO (though UA's OPO-EWR is summer seasonal). You might be able to do the same with TAP, though I'm less familiar with their pricing.