Can't really comment on the Rothschild issue, don't know what the Saudis say in response to that.
But regarding the matter of Wahabism and Daesh, I have come across such reports a number of times. The "Salafis" argue that this and many other things were fabricated lies against Muhammad Ibn-Saud and Muhammad Ibn Abdul Wahab.
While I don't have much reason to believe either story, there is one fact that does give legitimacy (to at-least a small part) of the Saudi argument. From what I have studied of these terrorist groups, they have two most significant foundations which are used to justify their actions.
One is the creation and enforcement of a Khilafah on the whole world, even on peaceful non-Muslims. They consider this as a part of Deen or a responsibility from God to fight until this becomes a reality.
Second is the concept that all Muslims who are not actively striving for the creation of a Khilafah are sinners (or have even become apostates), and until they do not strive for the cause they will remain as sinners/apostates. Their doctrine says that, leaders of Muslims nations are on the payroll of Western governments and now it is a duty of all Muslim populations to rise up, violently fight against their governments and overthrow them, so that the first steps for the creation of a global Khilafah can be taken.
Daesh and Tehrik Taliban Pakistan follow this ideology. Hizb-ut-Tahrir might not be a terrorist organization but apparently a significant portion of them believes in this doctrine too. Al-Qaeda, on the other hand, are for the most part concerned with Western targets than overthrowing Muslim governments.
The first point might possibly be a part of Wahabbi ideology too (don't know enough to comment on this) but the second point is definitely problematic. The factor in Wahabbi interpretation of Islam that is most contradictory with the terrorist ideology, is the concept that the Muslim populations do not have the right to rise-up against their rulers even if they oppress them. This fact is obvious in their societies.
The Wahabbis argue that they come to this conclusion because of Hadiths of the Prophet regarding this matter. This opinion was held by Ibn Taymiah and later following in Taymiah's footsteps by Muhammad Ibn Abdul Wahab too.
These "Salafis" blame (1) the Pakistan scholar Syed Ala' Maudoodi, who was instrumental in the creation of the concept that it is the responsibility of Muslims to "Aqeem-ud-Deen" i.e. "establish" religion over the world, and (2) Sayyid Qutb, a leading member of the Egyptian Muslim Brotherhood, who apparently was instrumental in the evolution of Maudoodi's interpretation into the shape that it exists today among the terrorists.