Is there any way to keep track of the medium price of STEEM being used for the conversion in progress?

That's a good question. I will take a look into the Steem source in the coming days. I guess it just depends on the median price at execution time (exactly after 3.5 days).

Also, maybe a calculator that demonstrates the profitability of the conversion based on the median price of STEEM from the prior 3.5 days?

I like the idea! Will think about implementing something like that in the conversion dialog ;)