If you have a spot where a Philodendron is happy, that's almost surely not enough light for Jade (unless the Philo happens to be P. bipinnatifidum, tree Philo. Those do enjoy some direct sun.) Rubber tree would also prefer some direct light.

Leaves that fall off don't usually propagate for me either. To be successful with that, a healthy leaf should be removed. After that, let it callous (dry/heal) at least overnight so it's much less likely to rot. Once removed from the plant, the leaf has no need for any moisture until some roots grow. You can watch that happen without putting the leaf anywhere near a pot, in a sunny spot. Once roots start to appear, lay on surface and mist the roots daily, without getting the soil soggy. As they grow more, mist a bit more, until you eventually just water the pot normally, once the new little plant has a root system going well through the pot.

Fertilizer is not medicine, and often too strong for struggling plants. If unable to perform photosynthesis well, because of insufficient light, nutrients can't be used. The method of misting the stems is very unorthodox, at least for a Jade (or any kind of succulent.)

When you water this plant, have you been removing the inner pot so excess water can escape? These plants do well in an unglazed pot that helps the soil dry more quickly, and allows more oxygen into the soil.

As Tiffany pointed out, the leaves should be healthy to begin with to grow new plants from. Can't tell if yours were, but ones in your photo look like they are rotting in wet sand (?).
What worked best for me, is leaving leaves just sitting on surface, the roots will 'find' way into the mix. I don't even spray-mist them & they will root.
Works with many other succulents.

Gollum, leave above, plants few month ago below:

A light reduction, either in intensity or duration, can cause leaves to fall. In most plant species, any given leaf will only be able to function efficiently if the amount of light it receives remains within a fairly narrow range. IOW, if we graduate light intensity on a scale of 1-10, leaves accustomed to a light level of 6, might only be able to function at levels between 4-8. Exposed to light outside of those parameters, the plant might shed the leaves and replace them with new foliage that comes online accustomed to current light levels and able to function efficiently at those levels. Individual leaves are usually quite a bit better at tolerating a change in light that finds them getting MORE light than at tolerating LESS light; so, that 6-rated leaf might better be described as being able to tolerate a level of 4-9 in most species of plants.

Leaf abscission also occurs as a drought response, which can be caused by under or over-watering, and root congestion tends to cause leaf loss proximal to (toward the root to shoot transition) the growing tips of branches, leaving the plant looking a little poodleish, with most of the growth concentrated in poms of growth at branch/stem tips.

The issues most important to growing this plant well are favorable light/ temps and a soil you can water to beyond saturation, whenever you want or need to, w/o having to worry the soil will remain soggy so long it compromises the health/ function of the root system. Maintaining a healthy root system is a prerequisite if you are hoping for a healthy plant.

Al