You are on the right track.
The weight will come off, (slowly), as long as you try to watch what you eat.
As far as speed goes, Who cares? Are you working hard? Isn't that the important thing?
Your distance, and speed will improve with time on the bike.
Learn to spin the cranks, do some quicker, (for you) type rides, and mix in some slower longer type of rides.
For a few people, cycling and weight loss come easy. For most of us, it takes some time and there are few short cuts.
Good luck, and may you always have a tail wind.