Hi there.
Looking at https://steemworld.org/@starworld, I see you received total of 701steem transferred and you sent total of 20steem to like resteem bots few weeks ago so that is why you only have 680steem in your pocket.
For the curation reward, it is based on the timing when you upvoted the post and how much power/value you have on that upvote comparing with every other upvotes. You are upvoting many posts, thankfully, and your voting power is drained to 6% so your upvoting value is less than a cent which may be much lower than other upvotes and results to low curation reward.
Voting Power recovers 20% per day so I suggest to recover your power by stop upvoting for 4days. 100% upvote will use almost 2% of your voting power so is recommnded to do 10 upvotes a day if you are giving 100% upvote or decrease your upvote value on each post if you want to upvote more posts.

I agree with you that there is a glitch on the internal rate to calculate the account value. It is nice to look at third party services like steemworld to find out the real value using the market price.

I hope this helps.