Go nuts on the main, loads of sticky white rice, keep the meat lean but tasty and flavour the rice for added fun! Maybe something like a tasty sweet and sour chicken om nomnom
Keep at it mate, 18 days sounds like an age, but after 16 weeks its nothing and it would be such a waste to throw it all away. The cheat meals now are still far enough away from the shoot to not have an adverse effect. Infact if they give you a bit more get up and go, and restore your resolve they will probably be more benefical then not having them!
Not long now.