Speaking from experience and having seen a few of these data points personally (possibly over-indexed on a small amount of data), often this comes down to making a choice of 220 with a 50% utilization vs 165 with 70%. Pretty much the same revenue for the company in the end, but with enough slack to put some extra short term gigs in there. Alternatively, in a situation where the company is confident of higher utilization, getting long term work, locking in a higher rate later, or being able to add extra bodies to the contract this is about $130 at 90% utilization (52 weeks - 4 weeks leave - 2 weeks public holidays). All these are common in .au govt contracts.

The mentioned 80-120 range seems like a feasible answer to this. Push for more (or strong bonuses) if utilization is generally high. Obviously the 140% depends a bunch on location / taxes / cost of doing business etc., find out what these are in your neck of the woods and exploit it to negotiate your salary.

I don't think working back from your bill rate to your W2 FT comp is ever a good idea. You're as likely to under-sell yourself as over-sell. It is not your problem if your employer can't make a unit economics case for your comp; your comp is what the market says it is. Firms can and do keep people on staff that are on paper not worth in billings what they cost to keep around, for all sorts of reasons.