"...you are giving me advice on a relationship that I ended 20 years ago."
No, I'm not. Not only am I aware that this is a long ago relationship, I'm entirely uninterested in it except as the saucer that holds your stupid.
"I am only asking when does it become abuse?"
This is the part I'm interested in, because it's a ridiculous lens with which to view relationships. It never becomes abuse. We choose, each and every day, to stay in a relationship or leave. If you choose to stay in a relationship that doesn't meet your needs, it's not abuse, regardless of the nature of the needs not being met.
"Men will abuse women by telling them that they love them and things will get better as soon as some event occurs. "
That's not abuse either. People tell self-serving lies all the time and sometimes other people believe them. We choose, each and every day, to stay in a relationship or leave. Having our own reasons for staying, even if it's general spinelessness or forlorn hope, doesn't mean we're abused by the lies we want to believe or the person telling them.
"Why can't a woman be abusive if she promises a threesome ,just to keep the guy around, but has no intention of ever doing a threesome with him?"
You seem to want so, so badly for this to be abuse and it just isn't. You stayed in an unsatisfying relationship for your own reasons. You didn't have to. No shackles, no chains, no indentured servitude, no abuse. Just you, choosing day after day to stay in a relationship that didn't give you something you wanted.
Stop trying to offload the responsibility for that onto the other person.