How low should I keep my reps? 1-3, 5-6, or 6-8?
You'll want to do some training in multiple rep schemes for strongman as it's going to test you both for max 1-rep strength as well as strength endurance. For example, one contest may have an overhead log press for max weight, another may be for max reps with a set weight, it will always change from one to the next. If you're great for your max rep strength but can't knock out more than 3 reps with 80% of your max without feeling like you're going to pass out, then obviously that weakness will hold you back in competition. So, it's a good idea for strongman training to be varied with different periods where you may work primarily on max strength, then later focus more on the strength endurance aspect.
How many sets of each exercise should I do in one day's workout?
Again, there's no specific "best' way to train at all times. I've seen strongman competitors who have marathon training sessions that last hours, I've seen some that only hit the weights and train events for an hour 3x/week tops. If you're talking about buiding a good base via the standards powerlifts, again, I'd suggest talking with Chewybaws about his experiences with the 5x5 program as a good starting point to add some mass and build that base strength. Powerlifting is a great way to really build your base before moving on to strongman, as having the time spent really pushing your squats and deadlifts will be very beneficial in crossing over to strongman competition. But, if you're still working on building a good base to get stronger and add more size, you shouldn't need marathon training sessions, just a good, solid program with reasonable expectations and you'll see thigs happen in due time.
Are there any reccomendations for abdomninal work, as in traditional core and abs or resistance ab training?
Initially, I wouldn't worry much about it. Squatting and deadlifting will help get you a great base for core strength, and strongman events where you're supporting weight such as via farmer's walks and yoke carries, you're going to be working your core even when you don't realize it. Rarely did I ever see much with strongman competitors doing much direct ab work, but when they did, it was usually just some heavy weighted ab work, like sit-ups with weight behind the head or held on the chest, rep scheme was kept low as there's no reason to do endless crunches for building a strong, supportive core. Being able to do a thousand sit-ups without resting won't do as much for your supporting core strength as being able to do 20 with a 100 lb. plate on your chest.
Are all of the preceeding questions answerable by reading up on powerlifting routines?
Can I expect to still build mass to make it to 200 lbs if I keep my reps low?
There are so many diferent powerlifting routines out there, it's best to keep it simple with something like the 5x5 program. Many of the other ones are much more geared toward experienced powerlifters who are struggling to put a few more lbs. on their competition lifts and won't have as much positive effect on those still building their foundation. As far as getting larger on lower reps, I gained about 30 lbs. with keeping my reps on most sets between 1 and 6, rarely going above. But, everyone responds to varying rep schemes differently, so it's not unreasonable to consider doing something that covers multiple ranges with some lifts done low rep, some medium to high rep. There's a lot of trial-and-error to find what you'll respond to the best, so expect that some things that SEEM like they'd be great may not work as well as you'd hope, and some routines that seem like they'd barely pay off may in fact give great returns.
I recently upped my caloric intake from 2,400 to around 3,250, my protein intake is equal to my body weight (163 grams) and I have started eating around 450 carbs a day, and 64 grams of healthy fats. Are these macronutrient levels sufficient or would it be better for my goals to follow one of Robert Cheeke's nutrition plans on here?
Sorry for my mouthful of questions and sorry if they are already answered by obvious sources. Thank you once again for the help.
Upping calories will definitely be the start of working to get bigger/stronger, I'd consider possibly adding more protein if you don't see things moving forward fairly quickly (say, over the first 3-4 months, it'd be reasonable to expect to put on 3-5 lbs. with a big spike in food intake and a good program for someone who hasn't been stuck in a plateau). There's always going to be varying opinions on macronutrient ratios as some will insist you barely need any protein (yet, I've never met anyone who had a large and impressive physique who did it on low protein, so that speaks volumes), some will suggest massive amounts beyond what most people will want to eat or need to take in. I myself don't need massive amounts of protein (usually no more than 1g per lb. bodyweight for gaining, but I need more to retain lean mass while cutting), but again, everyone's different and will respond differently to varying macronutrient ratios. Again, you're going to have to do the usual trial-and-error to find what's best, but so far, the plan of attack you have for food intake seems like a fair starting place.