Does COPD get worse in the evening hours?

My Sympathy to your family on the loss of you mom. Then a thank you for stepping in a helping your dad. Truly you are a gift! Being a caregiver or just a helper in some ways can be very emotional and physical, please take care of yourself also.
I can relate to your dad, I am stage 4, but still do pretty well. Night time can be a challenge and probably a little more for him. From my experience with helping with my father and now myself, these are the things I have figured out that makes the nights seem harder to breath, maybe my experience can help or give you some ideas.
Environmental changes: At night as the temperatures this time of the year cool off, then our AC's are not running as often moving the air with in the home the same it does during the heat of the day. This makes the air feel heavy to me, so ceiling fan and/or floor fan goes on. Does not have to blow on me, just need the movement giving the air a little "airiness" lol. Then there is the humidity or lack there of, either to heavy or to dry at times. To test for something like this, first I purchased a hygrometer, under $15 many places. With in 5 min. you get a reading of the humidity level in the home. Paid close attention to what it was when breathing easy to compared to breathing harder. For me 40% is best, but 35 to 45 is about all I can feel good with. Yes, a humidifier and dehumidifier was needed pending on the time of the year. We live in GA to give you an idea. The final thought is; in the evening your dad is thinking and missing your mom, plus feels alone, then chronic illness tends to make anxiety, panic and depression a little worse, these all can make it feel as if you can't breath also. IF you think this might be happening, would be a good idea to chat with his doctor and see if there is something they could help him with these, meds or therapy.

Hope some of this was helpful I so wish you and your dad a lot of luck.

I can't thank you enough for your feedback. I will certainly try to see about the humidity issue. We live in NE Texas so it's a problem! It was 103 today. I agree with you that he is probably lonely and scared at night. Again thank you for taking the time to respond 💙