You should try to stick to the exact research question answered, and avoid including your own personal interpretations - if people believe that your paper is relevant they will come across those in due course.
The same applies with the methodology - you could, for example, state that you used chromatography as part of the experiment. If somebody decides that your paper is relevant, they will find out exactly what type of chromatography you used in the method section.
Fitting all of this into a very restrictive word count can be very difficult, and it is a very daunting task. An overlong abstract is one of the easiest traps to fall into, so the key is to give yourself plenty of time.
Start writing an abstract without worrying too much about the word limit, making sure that you include all of the information that you believe to be relevant. Leave it for a day or two and then you can start upon a harsh edit.
With fresh eyes, you will see that some of the information is irrelevant and can be cut. You can take out some of the descriptive words and chop sentences down to their bare bones.
On the other hand, if your abstract is excessively short, then you have probably missed a lot of information out. Re-check, and see you have missed anything out, referring to your outline if you are not sure.
You can also ask another student to read it for you, as an independent assessor. If they cannot make any sense of your abstract, then it is back to the drawing board.