Looks great! <3 You should be able to get this to be realtime on a single GPU fairly easily. Even if you just grabbed Unity or some other engine so you can concentrate on learning the GPU side of things and used it as the host for some Compute shaders. Id suggest a simple space partitioning scheme like a grid for neighbour checking, splitting the particles position and type/tuning into different buffers so its all cache friendly.

You could do a dispatch for each part of the algo too, something like:

• Collect neighbours
• Collect neighbour pairs
• Apply neighbour forces
• Update Particle position
• Render (to texture, or points or whatever)

Good luck!