I'm spitting into the wind here, because the norms of temp-to-hire are simply not the norms of contracting and probably never will be, but, broken record: your contracting rate is wildly higher than your FTE salary. 2x would be a lowball.
2-3x base pay is a rule of thumb I've heard. Generally speaking however, most small software development companies are around $150/hr+ in practice.
If the question is "should I freelance or take a full time job", that's a much bigger, more involved question.
where there's a general expectation that a w-2 earner will be budgeted for years into the future.
The 2x doesn't come for free nor is it just for PTO & health - it's paying for all the non billable time generally spent marketing, prospecting, qualifying leads, creating proposals, paying for time to proposals that never result in paid work, etc.
A typical independent consultant or freelancer only does billable work 50% of the time.
To answer your question as to "should you?" - it depends on your goals. Contracting versus standard employment is not just a financial, but a lifestyle decision.