If your intention is to fade, you're best not to offer explainations.
As I suspect that those inviting you to dinner and other social functions are from your own congregation, they would likely already know that you have been abscent or 'inactive' so no further explaination should be necessary. If they still invite you, attend if you want but offer no excuses to permit them to back-out from their invitation.
You may consider JWs to be friends but WT indoctrination will have most beleive they have nothing incommon with you if you stop attending and are a risk to their faith if you develop views not in-line with the WT organization.
As you found out, whatever expaination you provide will be used against you. Most JWs really don't want to know why you're not attending as any explaination you offer will never provide a valid reason. They usually demand an explaination or action as they like to pigeon hole everyone with a label: Publisher, Elder, Pioneer, Associate, Marked, Disfellowshipped, Apostate, Wordly, Demonized, etc.
Of course, many witness love to gossip so any info you do provide will spread like wild fire along with whatever else they care to make-up about you or 'speculate' about why you've stopped attending.
As you provided a written response to one person already, there is no telling how many others that text was shown to. Written texts, emails, notes and conversations with more than one person really need to be discontinued as written responses maybe collected and retained for use against you while conversations which canbe overheard may have additional witnesses to what was said, even if what was heard is out of context.