It's going to be difficult to convince a physician who has already made up his mind despite any evidence to the contrary. Almost every credible site on the net acknowledges gabapentin withdrawal. To be honest, I think you need a doctor who believes you and has better knowledge of this medication, but I'm just some guy on the internet, and I can't/won't tell anyone what to do.

For evidence, I might start here: scholarly gabapentin withdrawal
Preceding a search with "scholarly" usually nets scholarly/scientific papers, studies, etc. There are other sources—PubMed, medical journals... some others here may have other ideas, or ask a good librarian...

But I have to add that IME, most doctors dismiss anything that comes from the internet. Some don't, but they're few & far between. It may or may not help to ask him outright what it will take in the way of credible evidence to convince him, but...

Whether a benzodiazapine is the best attenuator, I'm going by what has been offered to patients for withdrawl from other substances (i.e. opioids, alcohol) because some sources have compared gabapentin withdrawal to those in some respects. Also that the risk of dependence with occasional use is far less than with regular use. If you run into problems, I would think you'd find out rather quickly—before any dependence kicked in.

I know what this stuff (gabapentin) can do to you, and my wife is having issues with it right now, but as it has some therapeutic effect for her, it's a more difficult decision.

Ultimately, I think you have to do some digging and decide for yourself. We'll all be here to help any way we can.

Doc