An arbitrary line is better than no line. When most of Africa has an I.Q between 60 and 80 may as well cut it off, instead of say there's no problem when morons who breed like rabbits replace the productive citizens of your country.
Chinese immigration is good with me, although that doesn't mean you should bring in people with lower I.Qs. Making irrelevant shiting between whites and Asians a policy goal strikes me as kind of gross, because when white guys fetishize Asian female conservatism, as opposed to white feminism, it disgusts me. Also, Asian women are way more likely to irrelevant shit than Asian men, and I feel bad for Asian male immigrants to Western countries. Still, I'm ultimately cool with it. It's a small thing to be authoritarian over.
East Asians also have very low reproductive rates. People with higher I.Qs generally have fewer children, and far East Asian countries have it the worst in terms of population decline. The intelligence problem cannot be addressed with mere importation, something else will have to happen in policy.
Not equal, but yes, it's a factor. This is one of the reasons Islam is particularly concerning.
This also means theocracy is, to some degree, a solution, along with general social conservatism that pushes women into marriages or financial dependence. If intelligent people do not deconvert, religion does not necessarily have a dysgenic effect. If they can, it does. So no, in reply to your question about destroying religion, not necessarily.
I.Q probably is not a comprehensive standard for testing intelligence, and there are other positive personality traits and cognitive abilities that should be selected for.
I think any solution will have to be kind of interventionist, although hopefully in a way that causes as little pain as possible. Reproductive rights, sexual liberation, or conventional childhood may have to be infringed upon if you want intelligent human beings in a thousand years. Most likely, the interventionist solution will work whether or not you're dealing with white people or Christians, although beliefs about human dignity that surround reproduction may be harmful.