Bringing my 1 year 3 months toddler to Taipei in January

This is my first time bringing my 1 year 3 months lo to Taipei in January. I know it's going to be cold like 13° to 17°. I have a lot of questions to ask .. 1) What should I take note of when going winter country with lo? 2) I bringing one tin of milk powder there is it enough? I going for 9 days. 3) How to dress my lo so he won't feel cold? He hate wearing hats must I put the sweater hat on him? Worried he will take it off. 4) my husband only buy ticket flying over there, asking me to only bring 2 hand carry bags and other stuff if need buy from there. I think taiwan stuff should be safe to eat right? And baby clothes?? 5) how to survive 5 hrs flight with my LO on my lap? Pls advice me ....