There's a lot of information not provided here. From what you have provided, it doesn't sound like you're after specifics, but generalizations. Note that there are significant differences between 767's, just as with individual fields. You didn't cite a field elevation, so the first obvious choice is sea level. There are various engines found on the 767, and different wings, and engine/wing combinations. A B767-300 will have different performance with a P&W engine, vs. a GE, and a B767-300 will have different performance than a B767-300ER. A B767-200 will have different performance than a B767-300, and a B767-200ER (a -200 with a -300ER wing and engine) will have considerably better performance than the B767-200, or B767-300ER.
The takeoff weight will depend not only on field conditions (temperature, weight, runway condition, etc), but also on climb requirements, and may be weight limited depending on distance/time to destination and landing field requirements; one may be weight-restricted by multiple factors.
Figure 2000 meters as 6,500', and 3,000 meters as 9800', for simplicity.
This is from spaghetti charts, and doesn't take into account obstacles, obstacle climb, elevation above sea level, wind, slope, etc, so these are very general numbers. Calculated with a flaps 5 takeoff setting, which is the normal/default. Take them with a grain of salt. These numbers shouldn't be used for planning a flight, and are generalizations, with rounded figures, taken from the paper spaghetti charts, based on one model of the 767, and are one possible permutation only.
Takeoff distance only, not considering climb or flight path after takeoff, nor surface condition (factored in after)
Dry runway, for -5C, calm winds, sea level, 6,500' runway, B767-300ER, basic limited takeoff weight 377,000 lbs (MGTOW 412,000). With wing and engine anti-ice, reduce by 4,100 lbs to 372,900 lbs.
Dry runway for -5C, calm winds, sea level, 9,800' runway, B767-300ER, basic limited takeoff weight 407,000 lbs (MGTOW 412,000). With wing and engine anti-ice, reduce by 4,100 lbs to 403,900 lbs.
For a normal flaps 5 climb engine and wing anti-ice on, decrease weight by 5,390 lbs (rounded to 5,400 lbs):
Reduces takeoff weight on 6,500' runway to 367,500 lbs.
Reduces takeoff weight on 9,800' runway to 398,500 lbs.
Poor braking on a slippery runway, with no reverse, reduces takeoff weight by:
52,000 lbs on the 6,500' runway: takeoff weight limited to 320,900 lbs. (note that this is just 900 lbs above max landing weight)
55,500 lbs on the 9,800' runway: takeoff weight limited to 348,400 lbs.
Note that the reason for the higher penalty on the longer runway is because of a higher takeoff weight, hence more stopping distance.
Poor braking on a slippery runway with max reverse thrust, reduces takeoff weight by:
41,000 lbs on the 6,500' runway: takeoff weight limited to 326,500 lbs.
43,500 lbs on the 9,800' runway: takeoff weight limited to 355,000 lbs.
This best-case general value takes advantage of full reverse thrust for the rejected takeoff.
These values are further reduced by the V1(MCG) limit weights:
Poor braking, slippery runway, no reverse, 6,500' runway: data not available
Poor braking, slippery runway, no reverse, 9,800' runway: 240,200 lbs MGTOW
Poor braking, slippery runway, full reverse, 6,500' runway: 208,400 lbs MGTOW
Poor braking, slippery runway, full reverse, 9,800' runway: 355,000 lbs MGTOW
I believe you asked for OPT data, suggesting you wanted it from an OPT program, which I don't have in front of me, and those are rough numbers taken from paper charts based on error within a pencil width margin, calculated by an old, fat, balding irish guy with bad teeth and eyes far too close together, reading through cheap drugstore cheater glasses, under the influence of a can of Go Fast, too early in the morning...so don't plan a takeoff based on those numbers and generalizations. Also, there is more to consider, but in absence of detailed information, hopefully it's close enough. For a runway analysis, much more specificity is needed. Also, again, keep in mind that those numbers are limited to one particular version of the airplane (in this case a 767-300ER with GE CF6-80C2B6F engines. Values will also change depending on the brakes in use, and other factors). Also keep in mind that when ice and reduced braking action is thrown into the mix, due to variabilities in determining braking action, actual surface condition, etc, just because the manual says the airplane can takeoff at 355,000 lbs, don't bank on it. That value assuming full reverse works great until under full reverse the airplane begins to have directional control issues, for example, requiring coming out of reverse, and the predicted numbers are no longer valid. Because poor braking action is subjective, one may take longer to get stopped, meaning that one may be too heavy for the runway, despite the spaghetti chart prediction of happier times. When it comes to taking a grain of salt, extra grains may be a wise idea. Also, don't try this at home, avoid exercising immediately after eating, don't run with scissors, objects in the mirror may be closer than they appear, don't text and drive, and of course, stay in school.