I'm not sure he'd have much to worry about, there. Discovery is not a
fishing expedition. If he sued someone for defaming him, and their
strategy was to use the discovery phase to get his phone/email/etc
records, I think they'd be in for a very rude surprise, unless they had very specific requests for very specific records.
Not true, at least in US courts. I've been deposed more than once. A defense attorney can ask for all kinds of things. For example, take the matter of did he or did he not use Patreon funds to pay for prostitutes. He is on public record saying he did not, and he's being libeled. The defense attorney can demand ALL of his bank records, and go through them line by line making him explain what he was paying for and where the money came from. (I've been through a deposition just like that.)
The defense attorney can depose Evans, his wife, his family, her family, members of his congregation you name it. He doesn't have a choice not to answer, the defense lawyer can just have the judge dismiss the case.