70 SSAT + financial need is going to make the rest of your application critical for tippy-top schools like Exeter, L’Ville or Deerfield. If you’re applying to really competitive schools because of financial need, check out Mercersburg Academy, a competitive school that has been generous with aid to certain applicants.
I don’t know the most recent effectiveness of going Test-Optional at the boarding school level - perhaps someone else here can speak to that. There used to be a great thread that captured the results of boarding school applicants - having a brain cramp right now and forgetting the title but it was an annual list. We found that to be a useful resource.