If you are really starting from zero, I would suggest starting by walking a mile or two per day; no backpack needed to start, no intense resistance training program, no interval cardio (or if you do, think of it as doing extra at first). Just get in the habit of getting some exercise in every day. Do that for two weeks to build consistency and good habits, and I think that from zero, you'll start to see some changes in energy on those walks. After you build that consistency, then you can start to add a more well-rounded foundation. But doing something consistently starting right now (today) is the most important starting point. Better to walk a mile a day consistently starting right now than burn out or overstress yourself with interval training from the get-go, or to wait a week or two to start because you're trying to figure out the best plan.
For diet, it sounds like you've already done the most important thing, cutting way back on beer. Some carb reduction on top of that is fine, if you think of it more like mixing up the carbs-- make sure you get some quick- and slow-digesting carbs in there, favor whole fruit over sugar, no overprocessed crap, etc. Again, consistency is important; better to cut way back on the beer and make no other diet changes than to not do anything, and being in that habit is most important.
I wouldn't be too concerned about losing too much (or too little) weight. Eat good food to keep up with recovery and don't go overboard (and don't starve yourself, either). Most people who are out of shape, especially bigger guys, think they have way more muscle mass than they really do. A lot of out-of-shape 200 pound guys think they'd look ripped and muscular if they lost 15 pounds, and think they'd look scrawny and lose a bunch of muscle if they lost 20 pounds. In truth, the average 6' 200lb guy who looks like he's in "okay" shape on the outside is about 30% body fat (and guys who look chubby maybe closer to 35-40%)-- so only 140lb of lean mass. Those guys would be much more physically capable at 6' and 180 at 20% fat, or 170 and 15% fat, etc (example numbers; sure some guys at 6' have a larger frame, but most inactive people at 6' and 200lb are at least a little overweight). But again, don't worry much about the numbers and instead focus on fitness (i.e. your ability to perform and your level of health).