Remember that the resting potential is more positive than Ek. This is because there is a small Ina at rest. Myelination increases the effective membrane resistance, not the axial resistance. Myelin forms a tight seal on the outside of the membrane, thus limiting the membrane currents to the nodes. This increases the effective membrane resistance in the internodal regions.
Axial resistance is affected by the diameter of axon and the resistivity of the axoplasm.
Then you stated that the membrane resistance would also increase for the same reasons. Thanks, Generally speaking, no. The number of ions that actually flow is very small. However, in special cases where the extracellular space is very restricted and under conditions where a nerve fires many action potentials at high frequency, K may accumulate. When this occurs in the CNS, glial cells that surround the nerves, take up the K, thus helping to regulate the extracellular medium.