Your quilt looks lovely and the colors are great! You're doing wonderfully. Keep it up!
A couple thoughts:
I'm guessing your machine isn't inset into a table so that the bed of the machine is level with the surface of the table. This is actually the single most important thing that I felt really changed how I quilted. I spent about $20 and built myself a foam insulation table topper (
https://youtu.be/g14govA4pIM) following that tutorial except I also taped the vinyl down around the edges so that there is no exposed foam and the vinyl stays perfectly smooth. I even piece with this topper on - it's fabulous. It's really important to have no drag around the machine. Any drag will cause you to fight the weight of the quilt and that causes uneven stitches even with a walking foot.
You can build a temporary surround for yourself out of boxes, books, magazines, or anything to bring the level even with your machine, but any of those will still create a little bit of drag. Plus, magazines will sometimes catch on the corners and it's annoying, but at least those options don't require building anything. It really only took me a couple hours anyway and it was cheap.
My machine is a $250 Janome that I still love and I've quilted many quilts on it. It's certainly possible for you to do this on your machine! I see that you pin basted. Did you spray baste at all? My one experience with spray baste also left me with very uneven stitch length because the spray baste was causing so many more issues for me. If you did, you can iron it to set it better and I've heard that helps.
My machine doesn't have the option to lighten the presser foot pressure but slowing down and making sure my hands were really helping to keep the drag off the needle really helped alot. Lots of people use gloves of some type to help get better grip on the quilt - gardening gloves, grippy sponges, shelf liner, and they do make quilting gloves too. I love Machingers gloves.
You can also quilt with a pillow in your lap to raise the height of the quilt bulk closer to the table and machine. If you don't have something like your ironing board to the left of you, you should set it to the height of your table to help handle the weight. It's also good if you can figure out a way to prevent the quilt from falling off your table. If you're quilting on a dining table, maybe push extra chairs against the table behind the machine so the quilt doesn't slide off?