I have the Ergo and love it. My son still uses it at 3 for hikes. So comfortable, and my husband doesn't mind wearing it either. I actually wear it a lot more than him, he complains about sweat (since the child is right against you, I don't notice it as much. My son is lighter, about 30 pounds, almost 40 inches, but I can see it working for a while for us still. Also, you can carry your baby on the front with it for a lot longer, I did it every once in while until my son got too tall, probably around 32 inches or so.
I have never had problems getting him into it by myself (especially on the front), but I didn't get it until my son was 1. I guess the back would be a little more difficult, but still doable. And you can just wear him on the front if you don't have help.
I think this would work for your walks, I did an over 3 mile hike with him a couple of months ago, and had no pain except for sore feet on the way back (I need new shoes). Another option, if you are interested, is a jogging stroller. I used to always run my son to his babysitter.