Actually, just found the news dated July 4, 2016 (Russian).
The article states that SASCO had signed an agreement to resume the Ferry service from Sakhalin to Hokkaido using "Пингвин-33" as a ship.
Original Source on ria news (Russian)
Doing the sites on Kamchatka or Sakhalin on your own is possible but but personally I would not recommend it without good knowledge of the language and lots and lots of time.
To get to Sakhalin you could take a ferry from Vanino problem is you have to get to that port first. The same company provides cargo service from Vladivostok to Petropavlovsk-...