Jesus discusses the parousia in the verses before he tells them that the generation will not pass until all these things happen.
Which ever way one reads it - the Christian church is split over the passage which does not sit well when one considers that Jesus was actually warning his followers about a catastrophic future event...something that he would necessarily want to be unambiguous about.
Also - as detailed in Deuteronomy 18 - false prophets were to be put to death.
First of all there is not "the" Christian church, there are many Christian churches, and what a specific Christian church or as we tend to put it today, what a specific Christian religion may hold as doctrine can be very different to another religion, the classic example of this is Mormonism v any other Christian religion. I used the Roman Catholic church doctrine as it is still by far the Christian religion that claims the most members.
As you point out Lewis was an Anglican, but he was what we would describe as a "high Anglican" which meant he followed a subset of Anglicanism which is as near to Roman Catholism as is possible without joining the Roman Catholic religion.(Unlike quite a few of his contempories and near contemporaries his background is more than likely why he never converted to Roman Catholism.)
If you are a Roman Catholic there is no obstacle to faith in the verses you quote in the opening post as the RCC has long ago explained what those passages actually mean and they don't mean the end times would com about in the lifetime of the apostles. Indeed I would go as far to say that for any still existing variant of Christianity there can be no obstacle to faith in those passages since those religions will have already dealt with anything you may think of as an obstacle to faith.
Since Christian religions have existed for 2000 years there is nothing in their versions of "the" Bible or doctrines (remember they have different Bibles and different doctrines) that are an obstacle to
faith or they wouldn't have survived.
Many folk here can point to what are clear logical contradictions in the various bibles and doctrines, point out the horrific things the god of a particular religion not just turns a blind eye to but actually demands of his followers but that is about why people may not
believe in a particular god. But you used the word faith and not belief and in terms of a religion they have very different meanings. Faith is not meant to be proven, it is not meant to be evidenced, it is a belief without proof, indeed many Christian churches have been very explicit in making such a distinction and often consider it wrong to question the religion because it is meant to be about having faith.