I am sorry you're having a rough time of it AndyPandy.

It's good you're able to ice during the night when you're in pain. I don't think you should try to push through the exercises if it's causing more than mild discomfort.
You can certainly elevate when you're not icing, but the combination if icing / elevation is better when you're able to do both. Elevation is important because It is our lymph system that rids the body of fluid (swelling). So you want to get the fluid to the lymph nodes in your torso area so your body can more quickly process it. The lymph system works rather slowly on its own and much more efficiently with the assistance of gravity. The fluid isn’t draining into the hips, but contained with the lymph system and moving to the torso and lymph nodes located there. So elevate as often as you're able while lying down or sitting.
It is difficult for me to compare the recovery of a young child with a broken leg to that of an adult who's flesh was cut, along with soft tissue such as muscles, tendons and ligaments being disturbed. After which a prosthetic was inserted into the bone. It's typical for us as adults to to experience fear of re-injury, have concerns about not healing properly, or wonder why our recovery is lagging on. This is normal. A child on the other hand heals much more quickly. Kids naturally adapt to physical limitations quickly, and in most cases have experienced less trauma in life, so aren't as fearful, and are less likely to have the anxiety involved in movement that as adults we question. They don't worry about dislocation as many of us do in our recovery. As adults many of us need guidance in how to retrain muscles, exercises to improve our ROM and also to rebuild strength. Then there's adjustments in gait as it once again changes post TKR.
You need a healthy balance in finding the right PT. Therapy that's too aggressive can cause extra stress on the newly operated knee, leading to swelling, inflammation and pain. Gentle PT will focus on controlled movements that aid in circulation and soft tissue healing without overloading the joint. Stretching and low impact exercises should help restore ROM without triggering pain. A more gentle approach will encourage you, help you remain consistent and build confidence in the new joint and its capability along the way.
Each recovery is unique and while the philosophy we share here successfully works for many, there will be exceptions. Between the recommendations found here, your surgeon's recovery protocol and any physical therapy you may engage in, the key is to find what works best for you.
At not quite one month post op you are in a place common to experiencing post op blues. Please know that you're not alone, this is temporary and it will get better. Hugs Andypandy
@Andypandy