Here are my thoughts on your 3 areas of concern.
1 - Weight is a lot easier to shed than cancer.
2 - Every single dip you have taken in your life has been a choice that you made. Decide to NOT dip in the car.
3 - If you want to quit you can. We can help. Many have done it without "fake". I used damp green teabags sprinkled with cayenne, atomic fireballs, hard candy, seeds, gum, took picks, lots of different things.
If you are a man of your word then you will put your name on roll and honor your promise for that day. If you post roll on the morning of your 17 hour drive you are taking nicotine off the table. Quitting is a choice; so is using. Which will you chose TODAY (not tomorrow)?