there is no shaft seal available from volvo. im not sure about after market. make sure the hose clamps on the feed line are tight.

If the key getting stuck in the ignition? If it is, it sounds like the start control unit is going bad.

check the turn on wire (small wire) on the starter. I have seen several of those start to loosen up and cause the exact issue you are having. you can either replace the terminal or just tighten it down some