Well, it turns out I was wrong after all. The solution is actually pretty well known, and it's called the Pursuit Curve.

If you look at the parametric equation (4), you can see I was pretty close lol. But not quite.

The solution is equation (15) on that website, with general coefficients c1 and c2. We can use equatoin (18), with y0 = x0 = 0 to determine what we need.

I'm tired however, and now we have a solution for the curve of the path, we have solved the problem. Figuring out the time, distance etc is straightforward. I might try it tomorrow if I feel like it
Whoa.... Okay this is a big development... I've never seen that before. I wonder if some insight can be gained from that to get the 'simple' solution.

P.S. I think your DE's were correct. I dunno about the solution but your starting point looked okay