I doubt intense study would lead to jhana because there's still "too much going on" - even though the focus of what you're paying attention to has narrowed (it now excludes video games, Buddhism, family etc.) there's still a lot of perception, conceptualisation and thinking going on.
The feeling you feel afterwards (ignoring the caffeine) may relate to the fact you've narrowed your focus as mentioned above, and therefore to some degree stabilised your mind. Because of the narrow focus, which is now devoid of clinging and craving (because its former object of attention has been done, finished, let go of), you're experiencing calmness in the absence of craving and clinging. In time however this wears off as our habitual tendencies resume their prominence and that modicum of concentration dissipates.
You said, "It is this occasional feeling from time to time that supports my faith in the total elimination of suffering". I think that is a good observation and a good way to look at it.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)
"To argue with a person who has renounced the use of reason is like administering medicine to the dead" - Thomas Paine