Hi Mac010,
[b]1.I get exhausted after going through just 10 articles.[b]
Take regular breaks, break the task down in smaller parts.
[b]2. I am also having trouble stating purposes that are specific enough.[b]
What about a purpose of finding 'the purpose' or explore your thesis question, make a mind map with your thesis at the centre to start and get some ideas from that to discover a purpose?
I know that you are on the right track with syntopic reading (I did it in a seminar yesterday), I think you haven't defined clearly enough you purpose or direction 
I would go and start there. My feeling is once you get that right the rest should fall into place.
The steps we used in the seiminar.
1) state the purpose in the centre of the MM.
2) Radiating from the centre (approx 30cm) a new bubble( circle) with the name of the book/article, author, date of pub.
3) The line that joins the two circles, write down the words, phrases that seem to answer your question from each book going from one book to the next randomly opening pages and getting information out.
4) Lines radiating from your book/article bubble write in your own words what you wrote down from your list between the circles.
5) Once you have finished that do the same again from 3) but this time looking for themes from each book but writing this information adjacent to the relevant bubble.
6) Draw lines for things that are common or different between themes.
Hope this helps.
All the best.
Will ho 
