Ok....Here's my input on this...I'm no expert, but I've been also working to fix my credit report, so I'll tell you what I know...
First off, dispute any accounts you don't recognize or is reporting incorrect negative information. As far as your $12k credit card, I would contact the lender and ask them why they're reporting zero.
"the proportion of balances to credit limits on your revolving accounts is too high." would mean that you're using a very high amount of your available credit. It's always good to keep your balances as low as possible. If they're too high, then a future lender is going to see that as a risk.
Purchased by another lender either means that the account was taken over by someone else (could be like my car payment I had through one bank, they sold it to SST because they were getting out of the car loans.) If it's showing derogatory information and it's over 7 years old, you should be able to get rid of it by disputing the account.
Others will jump in soon and we'll help you get straightened around! Welcome to the community.
Sorry I can't be of more help, my mind is all over the place lately.
wfnnb is Wells Fargo National Bank.