I'm envious. You've got a great situation. A spouse who rides and is quicker than you. You always have someone to ride with and built in motivation to improve your fitness level. Ego aside, you're in a great place.
Keep pouring the miles into your legs, it takes years not weeks or months. Add some wind sprints in for speed and you'll get there! 2.5 years ago a 15 MPH average over 20 flat miles was an accomplishment for me. Now I'm knocking on 20s door. My
PR is 19.7 MPH during a flat course, 20 mile, Triathlon.