This reply answers a different question than the one you asked.
You wrote, “I have read that not having a willing partner is grounds for using ABC.” The answer to that is NO.
What the link you posted above asks is if your spouse contracepts and you do not can you still have relations with her. You would be a passive, uncooperating spouse in that case. For example, if you wife decided to get a diaphram or have her tubes tied and you tried stop her, but couldn’t, then you are not sinning if you have relations with her.
OTOH, if you say to her “ok, you don’t wnat to use NFP then let’s contracept” then you are equally culpable and are committing an objectively sinful act.
I’d suggest you get some sound documentation on NFP from www.omsoul.com first. Present her with fact that will answer any of her “fears”. Fear is often out of ignorance. If she has factual data and information on how NFP works she can see that it is effective.
Also, ask her to just take a class with you before deciding. Look up classes in your local area through your parish or go to:
www.fertilitycare.com or www.creightonmodel.com