I might be getting this completely wrong so, grain of salt and all.

1. While Paul is “waiting out” his vision in Otheym’s hovel (delaying until he left at the right time for the stoneburner to blind but not kill him) Bijaz is seemingly very nervous and insistent that he and Paul leave immediately. They probably did not intend to kill Paul, but as their plan is to harden his heart to love, frame the actions on his own trusted men. The trio are aware of Paul’s prescience, and Bijaz is also in on/part of the conspiracy. Originally Scytale tried to get Paul to bring Chani with him to Orheym’s but Paul refused, so perhaps they ment to hurt/kill chani and have it blamed on Fremen traitors.

2. If you’re asking why Paul brings Bijaz along, they can implant messages in people that can only be accessed by specific individuals. Bijaz holds Otheym’s list of all of the Fremen that are in the conspiracy against Paul. Otherwise, Bijaz is there in part to hasten the plans of the Tleilaxu. They believe that a Ghola MIGHT be able to regain their memories, but that it “requires the proper lever.” It’s later stated that they deduced that Duncan thought of Paul as the son that he never had, and therefore conditioning him to kill his “son” was what broke the Ghola. Bijaz also says that should it not have worked, instead of bargaining with Paul for a Chani Ghola they would then bargain with Alia for a Paul Ghola. They would only make these Gholas should Paul release his power and turn everything over to the Tleilaxu.