Thank you for being an advocate for your Dad and welcome to Mayo Connect! Are you also his caregiver? I think it is important to to have a helper/cheerleader/prodder close at hand for the first few weeks as much as possible.

Swelling in ankles and calves after hip replacement is totally normal, it is a sign that surgery has caused a major disruption to the body. Elevation is helpful in draining the fluid back towards the torso, where it can be absorbed and eliminated. Does he have a recliner where he can sit & elevate on a footrest, perhaps with a pillow underneath? You may need to get creative about placing (thin) support cushions, rolled towels, etc to ease his back.

Here is what I know about sitting versus lying down - too much lying down, or being inactive increases the risk of blood clots and pneumonia. So moving every 1/2 hour or hour, except during sleep, is highly recommended. Also, when sitting or lying down, ankle pumps, ankle circles and mild leg lifts (lightly assisted at first) should be done frequently. Also, he should be walking several times each day, with increasing distance from day to day

As for side sleeping - I understand - but does he have any restrictions about positioning of the operated leg? After about 2 weeks, I would lie on the non-operated side, with the upper leg bent & knee through ankle well supported by a firm pillow so it was elevated about 6-8".

Finally, you may be able to help with the swelling by doing some gentle "lymphedema massage" to the leg. You can find examples like this: