Charging will be set around 200mA by default (and not 500mA) and that’s because your input power supply must be able to deliver whatever the load takes + the charging current, otherwise the charger will shutdown and not charge the LiPoly battery, so this will be a requirement. For instance if your Pi takes 500mA, then your supply will need to be 700mA at the very least, I would opt for a 1A to give a hefty margin if the Pi spikes for any reason. If you use the jumper to set charging at 500mA then you need at least a 1A supply, I would add 300mA more for that safe margin. If you power your BBB through MightyBoost you should probably look for a 2A supply.
You should avoid touching/handling the circuit while powered. In extreme conditions Introducing shorts by means of sweaty fingers might cause MightyBoost to fail permanently. At most, hold the board touching only the outer edges while plugging the battery or USB. It’s best to have it installed in your circuit before feeding power into it.