...
I would have to do the onerous work and check my figures, but $450 - $500 is probably about my break-even.
I have spent some (on gold), so that will likely complicate my calculations. Perhaps I could value my BTC on a "FIFO" basis
Accountants' comments are welcome.FIFO relates to inventory valuation, not really useful for you (as the value is set at cost not actual market value).
Just treat gold purchase same as selling bitcoin. So add together all the $ spent on BTC (including fees etc), take away $ value of gold bought (at that time), then divide the result by the amount of BTC you're currently holding, now you'll see the average cost and you'll know whether you're in break-even position.
The above does not provide for any additional BTC you've earned or for any BTC spending (other than buying gold).