Keep loving them and know that this particular tough patch will pass. I had boys with the same age difference as you do and it was tough when the smaller one started becoming more of a boy and a threat to the older one. And when the older one stopped napping, I was really exhausted until I figured out that we could still have quiet time.
You can figure out what is going on. Usually I figured things out but not until after the crises but still I could use what I learned to make things smoother the next time. My boys needed regular routines, meals, snacks, naps or quiet time, and a lot of exercise at those ages. Music and baths saved many days from disaster.
I finally figured out that my older son had a problem with artificial flavors, colors, and preservatives, as well as salycilates (which are a natural preservative, related to aspirin and found in certain foods, including apples and tomatoes). The Feingold program, feingold.org, can be a lifesaver. It sounds tough to change your family's diet but even one less fit per day makes it worthwhile.
Every child is different but for us, taking out apple juice, tomato sauce and ketchup made enormous differences in behavior and also in toilet problems. Your kids could have a different problem, with dairy or gluten or corn syrup. It is worth figuring out and it never hurts to eat real food at several meals plus a couple of snacks that include protein.
Sometimes it was hard to get exercise but it was always better when we went out. The neighbors would peek out their windows on the rainy and snowy days that we were out but it was worth it. And if they got wet and cold, a hot bath was a special treat. Sometimes if the older one was a problem, we would find a ballfield and I'd have him run the bases. I still do that with my youngest and his friends if they act crazy in the car before I bring them back to the house. They think it is funny because I don't say it like a punishment, more of a challenge - like, can you run the bases three times?
At your kids ages, I made a rules chart using pictures. The kids (well the older one although I included the baby in family meetings) made the rules and I was pleased that my son knew what the rules were. We made up consequences - mostly loss of a toy, never time with parents or exercise. I really like the book "1, 2, 3 Magic." There are many discipline books and most of them have the same message: parents need to stay calm and unemotional. My kids are now teens and I still have to work at that. If Mom can't stay calm, neither will the kids. But don't be too hard on yourself, it is a really hard job. And remembering that you get lots of chances to teach the kids right from wrong helps.
The TV issue can be solved by turning it off for a whole day if there is a refusal to turn it off. This may be more trouble for you for that day but you can make it work. My TV locks with parental controls.
Friends have had lots of luck with early bedtimes. You can really change your kids' schedule by moving dinner to 4 or 5, followed by bath, reading, and quiet time. After 8, kids get a second wind and are really cranky which makes it tough for them to fall asleep.
I liked falling asleep with my kids so I never bothered having them cry it out. Kids left to cry have greater anxiety as adults (a Harvard study) and I can understand why they don't want to separate. If you lay down in a dark room with a story tape or music, it can be the nicest part of the day. They smell good after their baths and snuggle. I really like Jim Weiss cds. If the room is childproofed and the lights are off and everyone is quiet, they can move around a bit without you giving them any negative attention. Essentially you become very boring until they want to snuggle and fall asleep. I nursed so that was a great thing for the youngest but this worked for the weaned older ones too. If you want to get up when they fall asleep, you can. Or you can make up for the lost sleep for a few weeks until you feel better. We moved them to their own beds after they fell asleep but not all kids will transfer so you have to figure that out.
Good luck. I know it is super hard sometimes. Being a mom was much harder than working professionally for me. It can be exhausting and you don't get enough positive feedback. But the work is really important. You are raising men and we need more good ones!