Must a child who grew up not observant and became a Baal Teshuvah honor his parents who are not religious?
Yes, as explained above. Furthermore, even according to the opinions above who are lenient, one must still show them the respect that is accepted within secular culture and may not shame or cause them pain. Furthermore, even according to the lenient opinion, through showing them more respect than accepted in the secular society due to having become observant, this itself will encourage the parents to become closer to observance and to respect their child’s choice.
Must a child who grew up observant honor his parents who are no longer religious?
Yes, as explained above.
Should Baalei Teshuvah not live with or near their parents in order to avoid friction?
In all cases in which leading a Torah lifestyle will cause friction with one’s parents who are not yet accepting of one’s child choices and may get upset about his decisions to keep Shabbos and kosher especially in the home, then it is best for the child to minimize as much as possible the situations from occurring. Hence, it is better that he lives in a different country, or a distant area, and certainly not within the home of the parent.
 Minchas Shlomo 35; Shevet Halevi 4:17; Pesakim Uteshuvos ibid
 Likkutei Sichos 39:298