The hydrogen would have an infinitesimal effect. It is highly unlikely that any scientific instrument could detect it's effect.
The buoyancy of hydrogen comes from the mass of the air it displaces. So right away, we realize there's a problem. If you're in 1/1000th of an atmosphere, even a full spacesuit of hydrogen is denser than the air. It doesn't provide any buoyancy at all!
So let's give you the benefit of the doubt. Let's fill the space with pure vacuum instead. You said breathing was optional, right? Now consider your own mass. Perhaps it's around 100kg. That means your vacuum bubble needs to displace around 100kg of air. The density of air is roughly 1.225kg/m^3, meaning you'd need about 122 cubic meters of air. That's not the volume of a space suit. That's more like the volume of a room.
At a mere 10km of altitude, the atmospheric pressure is about a third of that, so you need around 450 cubic meters of air. At a mere 50km, atmospheric density is 0.002 kg/m^3, so you would need 50,000 cubic meters of air! That's getting into the volume of a supertanker!
Far better to use more typical means of arresting your fall, like parachutes.