Great news!! Trust me, it is not going to take 22 months. Prepare well for the interview and you will have your visa that day!
For documents, bring your original marriage certificate, birth certificate and your passport. Bring proof of your communication between submitting your app and February, but don't bring too much! Phone bills, skype logs - not more than 15 double sided pages. If your husband has been back to visit you, bring a few photos of his last visit.
Since you have some time, you can order your CAIPS notes, which may give some indication as to why they have asked for an interview, although they may say nothing (like ours). It's worth doing though. I have only heard of one couple in Accra who's interview was waived, so it's usually a formality to check the genuinness of the relationship.
Make sure you know everything about his family, names and birthdays. Know about his job, the city he lives in, and what it's like. Know your future plans. Answer the questions as if you're a couple "We are planning..." "We have talked about..." They will ask you questions about how you met, what you like to do together, what activities, etc. If you are a planning to have children, and when. Who of his family members you have spoken to, which of your family members he has spoken to, etc. They will ask you about your wedding; when, where, how many people, etc.
You will need to plan 2 nights in Accra - the night before the interview, and then don't plan to go home until the next day. My husband's interview was at 7:30am, he was done by 8:30 and then had to go back at 2pm to pick up his visa, so allow time for that.
Be relaxed, be genuine, just tell the truth and try to convey how much you and your husband are in love. I know what you put in your application, and it was very good, so I am sure this is just a formality and you will get your visa that day.
Congrats on the interview date! I am so happy for you! Now you can relax a bit and have a Merry Christmas!