Two Witnesses
In context, Deuteronomy 17:2-7 is talking about the sin of false worship. No one could be put to death for false worship unless there were at least two witnesses.
In context, Numbers 35:30-32 is talking about the sin of murder. No one could be put to death as a murderer unless there were at least two witnesses.
In context, Deuteronomy 19:15-19 is not talking about sexual sins. It is talking about any other kind of sin between two men, like moving back a boundary marker or attacking another man (those are the sins talked about earlier in chapter 19).
When the Mosaic Law is talking about sexual sins, it always mentions "woman" or "daughter" or something like that specifically (like at Leviticus chapter 18; Deuteronomy 27; Deuteronomy 22:25-27), and they don't mention two witnesses.
The accounts that mention "two witnesses" being required to convict someone are not about sexual sins. WTBT$ does not have scriptural support for their "two witness" rule.