Re: asking the dead to pray for us, this is minhag kol yisroel for all the generations. I know there are seforim that object, and say we should daven directly to Hashem in the niftar’s zechus, but the Jewish practise throughout all the generations is against them. They are like those who object to “machnisei rachamim” and “sholom aleichem”; the accepted halocho is not like them.
In particular, the Zohar explicitly rejects their objections, and says ודורש אל המתים refers to resho’im, who are considered “meisim” even when they are physically alive. It explicitly says when the world needs rain we should take a sefer torah to the cemetery and directly ask the meisim to intercede with Hashem to give us rain. It then says the local meisim who have been so alerted go to Chevron and inform those buried there about our plight, and together they go to the higher worlds and inform everyone there, and everyone prays for us, and Hashem makes it rain.
This is the Zohar, which klal yisroel has accepted as part of the Torah, so one who denies it is a kofer.