Collapsing after ten minutes with forearm tightness beforehand is a fatigue signature, and fatigue at two years usually means the arm is not supporting the hand, so the small finger joints are doing structural work they were not built for.
Check the boring things first. Bench height, so that with your fingers on the keys your forearm is roughly level with or very slightly above the keyboard, and your elbow is not below key level. Bench distance, because sitting too close makes you pull your wrists in and lock the forearm. Most people who are self taught are sitting too low and too close.
Then the shape. Play a five note block chord, all fingers down together, and notice the natural arch of the hand and the feeling of the arm resting into the keys rather than the fingers holding the hand up. That is the shape you want to keep in a scale.
And stop at the first collapse. That moment is genuinely useful information, not a failure to push through. Ten focused minutes, two minute break, another ten. An hour of continuous playing at two years in is how people acquire injuries and habits that take longer to undo than they took to learn.