ECtHR is the court. Note the "t".(as realistically the NHS is not sustainable unless you invade another country with oil fields),
ECHR is the convention that we signed up to.
But other than that conflation of the two, you are on the right track. IANAL but I cannot see how repealing the "religion and belief" part of the Equality Act could be compatible with ECHR articles 9, 10, 13, and 14. The Govt would have to leave the ECHR and then Parliament would have to vote to repeal the Human Rights Act before they could legislate away the Forstater ruling, because Forstater was about Maya's article 9 and 10 human rights as much as it was about the EA. Leaving ECHR would stop the TRAs from appealing the FWS ruling to the ECtHR. Leaving ECHR would also allow this or any future Parliament to repeal the GRA, the gender reassignment protections of the EA, and anything else that's only on our statute books because of Goodwin v United Kingdom (2002).
TRAs should consider carefully the consequences of what they are asking for. But we already know that they don't do that.