I choose 1. I just never noticed it being a common struggle until I came to the reformed side of things, and I see people admitting struggle in this area or pastors/teachers sharing counsel for those struggling all the time.
OK then. I don't think it is an uniquely or especially Calvinist struggle; however, I do think that it is the struggle of not a few genuine Christians; and many (perhaps like your own experience) who embrace the "Calvinist" interpretation do so because they were compelled to a deeper, fuller, more consistent grasp of divine revelation. This mark of a true Christian--a desire to know God in truth and to walk close to him without a false step--is already pronounced in them, already separating them from what could be described as a typical, often nominal Christianity.
I think people of similar bent, but whose search for that closer walk with God have not led them to Calvinism (instead, deeper into their own tradition's theologians; or to finding some other Confession), some of these end up with nearly the very same questions and doubts. The reason I think you have found them among the Calvinists so much could be because now you are surrounded by a greater concentration of people who are trained to have a passion for God. And that passion can lead to anxiety.
And, it is possible that the particular church, pastor, or sources of teaching one leans on can also be unhelpful when it comes to dealing with these anxieties. You may notice that while your original question used the adjective "reformed" before "believers," I replaced it with "Calvinist." I'm not being pedantic, nor am I challenging your own self-identification. But it is important to the discussion to realize that the
predestinarian definition of "Reformed" is reductionist, and wrong.
Today, the American church scene has a fair number of Calvinist-primarily-or-exclusively-meaning-TULIP churches and pastors, partly due to a "resurgence" noted a few years ago, connected to the YRR movement and a few prominent mouthpieces (such as JohnPiper). The way many of these churches and men promise assurance isn't Reformed, because they are not Reformed. Such people are
predestinarian after the manner of the Canons of Dordt, however they are more closely aligned with the pietistic strain of post-Reformation western religion and to Charismaticism, when it comes to describing and defining their religious practice.
Neither Pietism nor Charismaticism are especially
objective in their orientation to spirituality. They are largely
subjective, their focus being inward, looking within them for truth and for confidence. If they find what they are looking for--such as if they seek for tongues, or if they can count the number of days in a row they had and didn't skip their "quiet time"--their confidence is raised. If they imagine they should have come to a place where this or that sin is no longer such a strong attraction as it was, their confidence drops. If they imagine they might not be elect, because of X Y or Z, their confidence goes wholly out the window.
Such people are being encouraged to look at what they have, whether in gifts, in "fruits," or in doctrine; and to see in those things the
evidence of God's work; and if those things are not
increasing, the natural assumption is to doubt if the supposed blessings are actually sourced from the spring that never runs dry. But this whole approach is unReformed; it is anti-Reformed. It doesn't comport with our Confessed Faith as Reformed believers. It isn't even the faith expounded in the Canons, about which few who aren't in an actual Reformed Church that uses them know anything other than the acronym TULIP mediated through the teaching of a non-Reformed teacher.
Believers need to be taught to look away from themselves, and to take none of their assurance
essentially from their practice of religion. That their practice should and will be for them a thing of joy (if properly used) is an added blessing of faith; but it is not the ground of assurance. Assurance comes from faith, and nothing else. It's strength is from Christ as the true Object, so if I need any assurance I have no other recourse than to look to him. He is found (according to his promise) by all who seek him through his appointed means: the word, sacraments, and prayer.
Hence, the benefit of a faithful church and ministry, which serve the people of faith by feeding them on the word, and strengthening them by the sacraments, in the context of communal prayer (worship). The fellowship of believers (communion of the saints) is the garden-bed of spiritual growth, but isn't strictly speaking one of the means of grace. Feed on Christ, come to him weekly (daily!) and find him where he promises to be, believe that he is true to his word and take it/him to heart.
Then you will have real assurance. Contemn his ordinances, and you contemn him. Who should be assured then, other than the complacent sinner having confidence in nothing but (possibly) the means themselves apart from their End? Sin's effect is to deaden the fear of God, to be corrosive to divine means actually detached from proper union, to promote carnal security or despair, its opposite. In any but the elect, sin leads to eternal death; at least for the elect sin simply eats away at assurance which is not "so of the essence of faith," that faith cannot be without it. The solution is singular: turn back to Jesus using his appointed means of grace.