The spotting that appears after becoming pure from menses is not regarded as menses, because it is not ongoing bleeding. So, you have to fast and pray, and do wudu for each prayer.

The fasting person is enjoined to fear Allah and to do what He has commanded, and to avoid what He has forbidden. Talking to the opposite gender does not break the fast but it takes away from the reward of fasting.

If you are able to expel the food stuck between the teeth but you do not do so and you swallow it, then you have invalidated your fast. If you swallow the food stuck between the teeth involuntarily, then your fast is valid.