What Tosfos says is that, according to Rava, who holds later that Giluy Milsa by a Get is acceptable, that is only if his intentions are known to somebody (either the Shali'ach, his wife or the Beis Din) before the Get reaches his wife's hands. Otherwise, it has the Din of Devarim sheba'Lev, which have no validity.

Tosfos then adds that, if, like in our case, the man is doing everything that he can to prevent the Shali'ach from handing over the Get to his wife (rendering him an Ones), then min ha'Torah, it would not be considered Devarim sheba'Lev and the Get would be Batel. Nevertheless, since his intentions were not known before the Get was handed over, the Rabanan decreed that, since it is similar to Devarim sheba'Lev, we ignore his protestations and the Get is valid.

In the second Lashon, the Ri holds that, as long as his intentions were not known before the Get reached his wife's hands, it is considered Devarim sheba'Lev min ha'Torah, even if he is an Ones (see Maharam Shif).

If you still have any difficulties with understanding the Tosfos, please let me know and I will try and clarify them. I apologize for the delay in answering.

Be'Virchas Kol Tuv

Eliezer Chrysler