I'm not even sure from what position you are arguing from, but both of those statements (relationship with God supported by a visible church rather than requiring it, and Matthew 18:20) are fundamental arguments for Protestantism.
[0] https://www.catholic.com/magazine/online-edition/is-there-re...
If we can agree on that we are closer than you might think. And when I said "not dependent on the church" i was referring not to what I just defined above, but rather what in my head i figured (perhaps wrongly) you were more narrowly referring to.
To continue, at risk of muddying the waters that might have just cleared a little, the nature of the church (a divine mystery) is such that it can be known experientially while never being fully exhausted by human understanding