If you are 49 and have been sitting on a couch eating crap for the last 18 months like you have described then you wont have as much muscle as you think. Your main focus should be working on gaining mobility again and to lose a lot of fat.
Overall weight loss comes down to calories. You are currently eating way too many. If you're determined then you should be able to make some noticeable changes straight away.
Foods that don't have nutritional value aren't really needed at all. That's not to say you can't have a can of coke or a slice of pizza every now and then but you have to ask yourself how serious you are about losing fat. If you're serious then you need to start with eliminating crap food from your life.
Start with sugary foods and transfats. Soft drink, doughnuts, cake, chips, pizza, chocolate and basically all those foods that aren't real foods need to go.
Instead focus on eating good food sources like beef, lamb, pork, fish, chicken, eggs, rice and plenty of vegetables and fruit. Most vegetables are very low in calories but high in micro nutrients. Good fats generally take care of themselves with the protein. Fat from fish for example is really good for you and if you cook in olive oil or coconut oil again you are getting in healthy fats. Nuts are also good but they are calorie dense so don't go overboard.
If you feel like a snack go for a piece of fruit rather then a snack bar or other such crap.
Drink plenty of water. Start drinking water as soon as you wake up. You should never feel thirsty .
Be careful with bread and milk. Milk is high in protein but it also contains lactose which can have a bloating effect. Some milk in your coffee or on your bowl of oats is fine but never actually have it as a drink.
Some bread is also fine but I wouldn't recommend eating too much of it for the same reason. It can cause a bloating effect.
You don't need to count calories but it can be helpful to do some food tracking even just for a week. It can be a huge surprise to see just how much or how little of certain macros you actually have. Also once you see what a weeks food looks like it becomes very easy to see where to cut the calories.
myfitnesspal is a good accurate food tracker.