This is an article about the current distribution of nuclear weapons:
https://tinyurl.com/2vfb9ak8
From memory, this situation on the NATO side has been like this for years and has not changed.
You will notice that Russia already has missiles adjacent to Finland, so who actually is the provocateur?
I had been reading an article, in which Putin is reported to have said, "The NATO membership of the Nordic nations poses no direct threat for us … but the expansion of military infrastructure to these territories will certainly provoke our response". I interpreted "military infrastructure" as nuclear missiles.
Yes the map you posted does show Russian nuclear deployment near the border. I'm wondering if this predates Eastern European countries joining NATO? In which case, it isn't near the original border between the Soviet Union and NATO. If NATO expands Eastwards, should Russia be expected to move its missiles further back?
Going by Putin's comment that if Ukraine joins NATO it may try to take back Crimea, which could lead to NATO being directly in conflict with Russia, and given the possibility that as a NATO member, Ukraine could host US ballistic missiles and US troops, it is understandable that Russia would seek written guarantees that NATO will not allow Ukraine to join or put military infrastructure near its border.