This sounds like an excellent report, zenbooster, if you are finding "states from pleasant goosebumps to ecstasy several times," and the sound charism, which means you are likely to be making it to the 3rd stage of samadhi.
Regarding when to shift focus in the meditation from the breathe to the charism, I start with light attention upon the breath and when the charisms arise I might switch my focus to the charism, or I often find that my awareness can include a number of items once the charisms arise, so I look at the charisms as a multi-sensory symphony which I attend to, while relinquishing my attention to anything that involves the physical body and the physical senses, such as the breath.
Regarding posture: I never found full lotus conducive to depth in meditation, but crossed legs without placing one leg on top of the other has been very conducive for me to depth of the 4th stage of samadhi. However, to get passed the 4th stage to the deeper 4 stages of samadhi I found lying down meditation works best for them, because the deeper 4 stages of samadhi are in my experience out-of-body, so getting deeper requires meditating lying down, and I do that after my evening session of sitting meditation just prior to bed, then I lie down in bed and continue my meditation lying down, this typically results in an OOBE.