I will have to maintain private health insurance
Not really, if you do want get it i will recommend from medicover or damian they both operate together and have best health services for 5200 pln a year and also cover overseas for 30k euro and they have doctors who speak english.
The next time (hopefully soon) we want to stay in Poland and travel around Europe for up to 2 years.
yes you cant leave poland/eu for more then 6 months in 2 years to apply for your permanent card which is a requirement if you want polish citizenship.