Watts are indeed a measure of magnitude. Kilowatt HOURS are a rate (that's what the 'hour' part is, usage/time).

In any case, there are about 720 hours in a month (30-day month). So if you ran your 1k light 24 hours a day, that'd be 720 kilowatt hours. If you want to stay below 3000 kilowatt hours, then you could use as many as four 1k lights running 24 hours per day (but basically nothing else).

If you're using just one 1k light 16 hours/day, that's about 480 kilowatt hours, leaving you 2520 kilowatt hours for other stuff throughout the month. That comes out to about 84 kilowatt hours of 'spare' (non-light) useage per day, or about 3500 watts of constant useage. Since some months do have 31 days, you'd probably be safest using no more than 3000 watts on a constant basis (plus the 1k light 16 hours a day).

Check my math, but I believe that's correct.