Hi, Sorry to hear about your boy. :( Seedy toe
is when the hoof wall seperates from the pedal bone. This tends to happen if your horse has had chronic Laminitis, or a trauma to the sole at the front of the foot.
The whole of the front hoof is normally removed, so the cavity is completley exposed, then it can be treated with some kind of iodine or some use Eucalypctus oil. White Line Disease
Is a fungal infection of the hoof, so most probably linked to the thrush he's had. This normally happens if a horse is kept indoors alot of in a very muddy field. A crack will normally appear and gradually become wider, it eventually fills with a really foul smelling crumbly material. Its caused by fungi or bacteria entering through small cracks or nail holes in the hoof.
If your farrier recommends cutting the infected part of the hoof away, your boy will probably have egg-bar shoes , which help support the hoof.
Let us know how he goes.