Congratulations on the weight loss so far.
If you haven't spoken with a nutritionist lately, it might be worthwhile. Possibly, there might be a handful of key changes you could make regarding your intake that would make a world of difference.
As for the exercise, don't discount the utility of strength training, either. For everyone, but particularly for those of us north of 50yrs of age, retaining muscle mass and bone density becomes an increasingly tough challenge. Plus, additional muscle (in place of fat) helps increase your metabolism, burns more calories to maintain, takes up less space (so clothing fits better, even without a weight drop). Also helps guard against injuries, as well, being stronger and more flexible.
If you haven't done so, already, I might suggest having 3-4 days per week in the gym, where you engage in a solid 30-45mins (or more) of strength exercises that challenge the whole body. (In addition to whatever cardio you're doing on that day.)
In time, you could get even more benefit with designating a given day as (for example) "leg" day or "chest" day, focusing mostly on exercises hitting those key areas, with suitable recovery time following the "focused" day before you hit the same muscle area hard again.
As for the cardio: boosting the time you spend and the intensity of the effort can yield good results, in terms of burning more calories.
If you walk on trails, strive to incorporate routes that involve more hills, as well as boosting your speed.
If you walk on a treadmill, consider leveraging the elevation ability a treadmill offers. You can alter the incline, change up your speeds, lengthen/slow your stride, etc, to boost the cardio benefit of the session. Done in an interval sequence, time on a treadmill can be much more challenging than a modest-to-moderate effort.