I went through all the links. Thanks for providing them.
The first thing that needs to be said is that all these links are opinions, and none of them is statistically based.
And thats the reason why in these four opinions you have data varying from 17% to 80%.
Whatever claim is made in these opinions, the source of their data is not mentioned.
Nevertheless, none of the statistics claim anywhere close to what you are claiming.
You say: "This why 50% of married people now have affairs"
Since a marriage is between two people, basically what you are claiming is that at any given moment in any given marriage, one partner is presently having an affair (on average).
Statistically speaking that would translate to: "in 100% of all marriages, one partner has an affair". (on average)
If you would to have a look at registered statistics, such as those which are listed on Wikipedia, you will find much lower and far more realistic figures.
Unfortunately the data on Wikipedia is a bit outdated. They are however real statistics and properly documented.
One of your links mentions a source "Journal of Couple and Relationship Therapy", you can find it here:http://www.statisticbrain.com/infidelity-statistics/
So lets focus on this for a second.
The focus must be on line 4&5
From here you see that (male) - 1 in 5 marriages, the man has strayed and (female) 1 in 8 marriages.
So combined, you can say that on average in 20% of marriages, one partner has strayed.
If I were to translate that to what you have claimed, the correct wording would be: "This why 16% of married people now have affairs"
And actually this is also untrue, because you insinuate that people "now" have affairs.
None of the studies claim such a thing. In particular the study we are looking at claims that "have strayed at least once during their married lives".
This insinuates that this could have happened in the past, or in a previous marriage, but it doesnt say it is presently going on or is repeating itself.