Very sorry to hear about your father. It sounds like he had a large stroke. Unfortunately, predicting recovery from a stroke is very difficult - notoriously innacurate. Since he is
13 days out from the stroke, it would unlikely that he will get any worse at this point, but how much he improves is near impossible to say.
I frequently compare our ability to prognosticate recovery after a stroke to other scientific fields such as predicting the weather or predicting economic trends - we simply are not good at it. All I can tell you is that I have seen people in his condition do very well - improving enough to walk, eat, speak. I have also seen people make little to no improvement. It would be helpful to chart his progress with a diary. You should expect to see a fairly steady rate of improvement for about 3 months, then the improvement slows down for another 3 months, and then typically by 6 months there is little to no improvement thereafter.
The best thing for you to do is encuorage him, be with him, and work extra hard with him on trying to recover the function that he has lost.
With regards to the swelling, in my experience this is usually caused by a lack of vascular tone in the affected limb, causing leakage of fluid into the soft tissue. The best way to treat this is with mobilization of the leg, elevating it above the level of the heart when he is sitting or lying, and using compression stockings to push the fluid out. The one thing that you must be sure about, however, and you must check with his doctor about, is whether a clot in the veins of the leg has been excluded. If he was immobile for long enough, a clot could form in that leg and cause swelling. That is a dangerous possibility. An ultrasound can quickly evaluate for that possibility.