You can wait until 6AM with the understanding that you may miss out. You asked what time reservations open and your question was answered. People have reported getting theirs after midnight. Choose what is best for you but with the understanding (and your own personal experience) that the information you were given by a CM could be incorrect.
You are eligible to book 60 days for the first part of your reservation. For a split stay, you cannot book the second half until 60 days from the start of that portion. Feb 17 is 60 days from today. If the second portion of you split stay starts Feb 18 or later, you cannot book for those dates yet.