Prevent Macbook from Charging past a certain level
In short, no. Well, at least not without changing the SMC Firmware. 

The SMC (System Management Controller) is responsible for controlling a range of power-related functions (e.g. controlling fans, reading and responding to sensors, controlling temperature levels, the battery, etc). This is not something you want to mess with.

In terms of battery swelling, there are many factors that contribute to causing this and one of those factors is time. For example, I was responsible for a small fleet of MacBookPro5,1 models being used by five staff members, all of whom had two batteries (so they could hot swap them as required). All of these batteries swelled over time, despite the fact these laptops were used off AC Power for most of the day five days a week. The fact these devices were not kept at 100% charge made no difference whatsoever!

In a nutshell, if you're happy using FruitJuice then keep doing that. But trying to force the SMC (or circumvent its function) is likely to cause you more problems than its worth.