From my side, I have got two what's app messages per week for every week so around 168 screenshots for 84 weeks (approx 13 pages on word document). I guess it should be the same for her.
Okay, that is way, way too much. You only want to include 2-3 pages in total.
For 84 weeks, I would go with 1 screenshot every 1-2 weeks, to give no more than 40-60 screenshots in total. You should crop out everything except the name and date and then paste them in a list on a couple of sheets of paper.
You could maybe each include 1 screenshot every 2 weeks, so that you're alternating them. For example, you screenshot one message for each of weeks 1, 3, 5, 7 etc. and she screenshots one message for each of weeks 2, 4, 6, 8 etc.
However, another problem, my wife broke her phone about 7 months ago so only has record of whats app messages from November 2017 until now.
Not a problem. You can use both yours and her screenshots from November onwards, and then just yours from before November.
As long as you have other pieces of evidence to cover the rest of the time, it doesn't matter if you only have messages from certain months.