First get PO on board. Choose the process that will push PO into the central role: Kanban, Scrum, XP(anything really). Work with the PO to create user stories, estimate and calibrate. PO should work with stakeholders to ensure that the timeline is realistic.
Get your team a proper training. Hire someone to do training on the tech you use. Get some courses from Pluralsight/Udemy that will be mandatory for everyone on the team. Extra day in month spend on training is not much but it will up-skill people quickly.
Drag in your manager. Get him into a meeting and ask for a guidance of the senior manager. Make him co-responsible, he might help with funding on the project. Cut features to absolute MVP. If nothing works, escape sinking ship.