You're doing a lot of work and that cannot fail to get you fit. However using high ratings will stop progress, sooner rather than later.Now i have no idea if that is good or bad or average for my age (42 and 14 and a half stone 5 foot 10 in height)
If 7k in 34 minutes (pace 2:25, 115 W) done at rate 30 is typical, your stroke (worth 115/30 = 3.8 Watt-minutes) is short and weak. If so, this can be due to belly getting in the way and/or nonexistent technique.
At your height and age you can easily pull a stroke worth twice that amount of work. The ratio Power in Watts/Rating is the work in each stroke, so on the erg we can see exactly what we are doing.
Rowing is all about the recovery, since this lets us rest and also puts us into a strong position for the catch so that we can do a lot of work in each stroke. The main points to look at are:
Recovery with hands away, swing, then a slow approach with the slide to the catch. This puts the shoulders well forward and the slide about 50 cm from the heels, so that you can use your legs.
Bad signs that make real work almost impossible are:
Lifting hands over knees
High feet
High drag
Slide near the heels at the catch.