Ripple owns 99% of the coins
Ripple is transparent about the XRP they possess in their quarterly reports.
Check https://ledger.exposed for live statistics about XRP distribution.
The Top 100 accounts (wallets) contain ~81% of the circulating XRP supply. Most of the wallets in the Top 100 are exchanges. The actual amount of XRP Ripple can spend not even close to 81%.
Regarding the 55 billion coins in escrow: Ripple can't touch these coins and uses them to support market makers.
Read more about the effect XRP sales from Ripple has on the XRP price in the Q1 2018 rapport
Check this article for an educating read 🎉