Is it ok to say Likutei Tefillos on Tisha b'Av?(I once asked someone about saying Tehillim and he said not to.). And what about Tikun Haklali?Do you know if there were any customs regarding these things?
I don't have a specific mesorah for this, but would suggest that you say the tefilah from L"T corresponding to Torah 67 in Chelek II, which is appropriate for Tisha be-Av. Tikkun HaKlalli should be no problem at all, esp. if you try to say it every day.