Approaching a roundabout, I'll move into the traffic lane proper at up to 50 metres before the roundabout if it's busy using the best gap I can find. I find it very useful to have a mirror on the bike using the mirror to check for an upcoming gap and doing a proper headcheck before I make my move. You'll find that all the roads with bike lanes have the same approach to roundabouts. You are legally entitled to take the lane and it is far safer than staying to the left and leaving the road open for the impatient types to push by you.
All of my inquiries re. Skeleton Creek Trail to Fed Trail have led to one answer, there are no plans at present. The only way that the two will be joined is via an overpass over the highway.
Palmers Road will be open in the not to distant future which will allow access to the Federation Trail from Skeleton Creek Trail, it will be a lot safer and easier than using Sneydes Road.
There is a way via Hacketts Road to get onto the highway exit to Hoppers Crossing. I've used it quite a few times and it is the best way that I have found to get into Werribee. It is probably a bit dodgy legally as the exit can be argued as being part of the highway on which it is illegal to ride but I've been passed by several police cars and they've ignored me.
Yes I know, my luck might run out one day but it's the safest route that I know of at present.