Dear Rod:
It appears that your wife is acting on he behest of her sister.
Only thing you can do is convince your wife to come back, find another job for yourself. If you are not able to find any job for yourself and earn money, her dreams of getting alimony/maintenance from you will be so so. Regarding the second child, you need to take care of her by giving alimony for another 2 years till kid turns 18. At the same time if you are not able to maintain yourself at all, you can claim maintenance from your 1st kid as she is already earning member u/s 125 crpc.
Your wife's idea of kissing goodbye to 23 years of marriage is non-sensical, so is her idea of selling the said flat that you part 50% share of it. You both need to talk in private and sort this out than going to court where 35 somethings are judges and will feel embarassed themselves to handle your case.
Allegations are allegations untll unless proved in court of law. If you were taking that drink, couple of pegs, nothing wrong in it accepting outside of court. The problem seems to be something else, its not your drinking or your present joblessness. According to me, there has been good tuitioning to your wife by your wife's sister/friends/other relatives to take such a decision. Find out the root cause yourself before its too late, as there is no immunity against dowry cases or domestic violence cases or maintenance cases against you.
Divorce is not a joke, it will break the strongest of the people, Indian courts will ensure that you are destroyed.
You both are quite old, you should be in a position to be guide your children on how to lead life, instead of acting like buffoons and be wrong examples to children as well as society.