There are multiple schools of thought on how to interpret Revelation, but one that should be kept in mind when "assessing" it, is that one fully valid interpretation of Revelation is that it has NOTHING to do with our future at all. It is an apocalyptic book to be sure, but there is a pretty wide amount of scholarship that says that Revalation should primarily be interpreted simply as an invective against Rome, and has nothing to do with the end times.
The number 666, for example, could simply be a veiled reference to Nero- This article on gematria for example, shows that it was long known that Nero fits the description very well.
Additionally, a reading that says this book is about the then present struggle against The persecutions of Rome also fits the first rule of Hermeneutics well- a text cannot mean what it could not mean to the original readers.
Remember that by the time Revelation was written (probably late in the 1st century), Paul had been beheaded, Peter had been crucified upside down. The Jewish kingdom had been dispersed, and all Christians were already being martyred in the Colluseum. Christians needed to know that this was temporary. Things were going to get worse, but they needed to know that God wins.
As to the "mark," it is obvious from Scripture that anyone who takes the mark will be pledging themselves to the beast in a radical way. No one puts a mark on their hand or their forehead without wanting to make a clear statement. If it really is the mark of the beast, there is a conscious decision that will let you know.
Paul is clear that we are to be vigilant, and that we should be watchful, but he also cautions us against falling for "the stories of old women" and unsound doctrine. Revelation is weird book, but we don't have to make it any weirder by adding fanciful ideas to what it means.
At a a basic level, we know, from Revelation, that in the end, God wins. That alone is enough for me to concern myself with. Whether or not my credit card is going to be the instrument of the devil is Not the point. Whether or not I'm going to take heart from the fact that I know God is going to win is.