I think you need 3 components to your campaign:
1) Play lots of tournament chess (which you are planning on anyway) preferably against players stronger and much stronger (+200) than you.
2) Analyze your own games and those of your opponents (where the draw is made far enough in advance and you can find their games - over time you will have games that you have played against them).
3) A course of theoretical study.
In your game analysis you are looking to identify when and how you lose games with a view to fixing your problems. Feed them into a chess engine. Stockfish is powerful and free. ChessDB is a good free equivalent of Chessbase in case you have an old or crippled version. At this stage you are aiming to identify lapses of concentration, weak tactical ability / poor chess imagination and "drift" where you aimlessly let your advantage slip away (planlessness or bad plans) or that of your opponent gradually build up (poor fighting spirit).
When you analyze your future opponents' games you are looking to see what they play against your repertoire and look for chances to unsettle them and take the initiative. Prepare what you are going to play against their different likely possibilities and familiarize yourself with the plans appropriate to the position.
In your theoretical studies you are going to want to systematically address 3 or 4 areas.
1) Opening preparation. Decide which openings suit your style and available time for study. Very sharp, current openings will require a lot of work to stay uptodate. You may prefer to limit your required study by choosing openings where you can quickly limit your opponents good replies.
2) Every time you lose an ending or draw one you should have won make a point of going over the theory of that particular ending in something like one of John Nunn's books. Gratuitously study endings you are unfamiliar with. This may not pay off in immediate extra points from getting into these endings (although over time it likely will) but it will improve your general endgame play and in particular your approach to the endgame. A good example of this would be KNBvK.
3) Hone tactics. There are lots of books out there stuffed of tactical problems. Pick one and do a few every day.
4) General chess study. There are several book-series courses out there. The most famous is Dvoretsky's "School of Chess Excellence" series. No offence meant, but I think this is likely to be too advanced for you. I have several of these on my bookshelves but have never managed to read more than a few pages. Maybe when you are going for your IM or GM title ;-). Yusupov has done 3 series of 3 books each - "Build Up Your Chess", "Boost your chess" and "Chess Evolution" which I would recommend you start with. I'm a similar level to you and have actually worked through 2 out of the 9 books and felt I got a lot out of them. You have the time so work through them systematically.
Under the heading of general chess study you should also read "left field" books which will broaden your chess outlook. Example books would be Jonathan Rowson's "Chess for Zebras" and "The Seven Deadly Chess Sins", John Watson's "Secrets of Modern Chess Strategy", Willy Hendriks' "Move First, Think Later"