The typical JW uber letter. It's all about them, not you. You have left US and you have hurt US.
It seems to me either your mum or dad have let slip something to someone, or someone has thrown them under the bus for some reason over you.....and someone has stated something about the kids having girlfriends/boyfriends or seeing Xmas lights etc. In other words they have definitely come under outside pressure.
May I ask does your brother/in law shun you?
I cut out the quote above because as it seems your parents are sensitive, kindly types perhaps saying that to them may make them think....”it’s all about YOU, how YOU Feel/hurt typical Jehovah’s Witness. Prepared to sacrifice the world as long as you’re ok”.its all on their terms, if THEY have necessary family business they will call, if YOU DO ha!! Fat chance you’d hear from them (for most j-dubs, I don’t say in your specific case, there are exceptions I know}
Harsh? Yes. Surely. Ask your dad if it’s more important he’s an elder or your father. Sorry I don’t think you should ignore them. That’s just what watchtower wants.