I hope your other cat comes home soon. Having two cats myself, I know how you worry about yours.
I honestly don't think it will matter if you don't go to PT until you are able to drive. You've been shown what to do by your in-home therapist. That, and just walking around the house will be plenty of exercise for your knee at this stage.
Many of us did no formal PT at all, and had excellent recoveries. You see, it's not exercising that gets you your ROM - it's time. Time to recover, time for swelling and pain to settle, and time to heal. Your ROM is there right from the start, just waiting for all that to happen, so it can show itself.
I did go to PT a few times for my first two knee replacements, but after the last one I did no PT at all. I just let the normal activities of my daily living (ADLs) be my PT. I have had three excellent recoveries.