Is the intention, resulting from obsessive doubts about dispelling uncertainty concerning divorce, which the questioner mentioned to the Mufti of Gaza, considered valid in Islamic law? And should one take the fatwa from those whom the questioner directly met, or from the fatwa website?

Consult those among the people of knowledge and trustworthiness in their knowledge and religion, and act upon their fatwa, paying no heed to others. Direct consultation is better than correspondence. Beware of exceeding in whispers (waswas) and turn away from them. Seek Allah's help and supplicate Him frequently to be rid of them.