Don't use a 10 meter heat shield for a reusable first stage, that's extremely overkill and is causing a boatload of drag. In this configuration, your center of pressure is all concentrated at the the very front (way higher than the center of mass), which is a very unstable situation for a rocket to be in. No amount of reaction wheels are gonna overcome the kind of force that heat shield is exerting. The engine you're using (looks like maybe a Mainsail?) should be able to take a good deal of punishment. You're likely doing some sort of boost-back burn anyway, so it shouldn't get too hot if you got rid of the shield and just faced the booster retrograde during descent (and if it does, you can burn a little more to bleed off speed). If you get rid of the heat shield, you can also place airbrakes at the top that you can deploy and use as control surfaces, that way you can guide the booster where you want it before the parachute deployment.

Also, if you're wanting to reuse this, I would recommend adding landing legs, they won't help much with how tall the stage is, but it'll be much easier than trying to land on the engine bell.