hi allicec how are you? its me satchi. Its a good idea to split into two; Research Contributions and Further Work. To avoid repeating/summarising what you said in the earlier chapter conclusions, tailor your Research Contributions as overall contributions; while the ones in earlier chapters are conclusions based on the chapters (its like a big hamburger, and small hamburger; they are the same but they are different).
Further work, as I was told, can have lots of sub-headings; no problem, you just need to lead the reader into how the research can be stretched further.
hope this helps, and wishing you all the Best!!!
love satchi