Ok so looking at your current numbers 4 months seems to be plenty of time given what you are working with already I'd say you're weakest area right now looks to be the row. Which can be brought up easily enough whether that be from refining your technique or just rowing more.
1. Pullups -If possible I'd recommend doing most of your practice on rings or some type of handles that move. Or at least change your grip often. When I was deployed last year I took my dead hangs from 11 to 21 at a BW of 89kg's The biggest lesson here is to be careful of your elbows! I was using a regular pullup bar for the vast majority of my training here and I paid for it. Nowadays I can still hit 16 most days and I only hit pullups once or twice a week.
- The vast majority of my improvements came from doing the Chad Waterbury Pullup, Lunge Pushup program - Basically you start with 1 of each per day and add one every day for 60 days. You don't change the rest of your training. In 2005 or so I had good improvements using the Armstrong Pullup program but that program requires INTENSE dedication. Last year I wanted something fun. Both programs can be found online.
- Once I made my elbows crazy I didn't stop doing pullups just did them way less frequently than every day. I had one day of weighted pullups where I worked up to a PR of 45 kg's around my waist and a day of just bodyweight pullups
-With 4 months I'd try to work in at least 2-3 weeks into those 12 where you take a total break from pullups IE Weeks 1-4 Armstrong program, week 5 still training but no pullups at all, weeks 6-10 weighted pullups....etc
2. Dips - Never really tried to improve this number other than gymnastic ring dips but the same principle for your elbows, dont let them get to the point to where they are smoked that will really limit your competition training.
3. Row - My best 1000m is like the 3:30's and my best 500 was 1:31 so take my advice on this category for what it's worth. What I started with I don't even know, needless to say before I first discovered Crossfit I had never touched a rowing machine before.
- Technique refinement - through various online resources I found out that just sitting there and pulling on the handle for all I was worth wasn't the best way! Years ago like 2005/2006 CF had a series of rowing videos not sure what the availability is now online. Those and learning the "starts" really helped me shave seconds off my time
-However nothing will help you in this category other than doing it! One 1000m+ day, one 500m x 3 day with 1-2minutes rest...things like that.
4. Aesthetics - I personally have no bias against that but you'd probably get more information elsewhere. How do you stack up in this category right now? How does the competition stack up? Is it like a race to get as ripped as possible? Are the judges looking for symmetry?
5. How else are you planning on training for the next 4 months minus those 3 events?
Don't forget recovery! MobilityWod has some great videos on how to treat smoked elbows and shoulders but you need to make sure you don't let them get smoked! Just almost smoked! Nothing wrong with programming in a deload week or recovery day into your week. It's not as glamourous as the other stuff but necessary with all the rowing, dipping and pulling.
"And for crying out loud. Don't go into the pain cave. I can't stress this enough. Your Totem Animal won't be in there to help you. You'll be on your own. The Pain Cave is for cowards.
Pain is your companion, don't go hide from it."