Please help- need guidance- my manager quit and suddenly I’m the only one in my HR Dept.

For context, I’ve been with this company for about 6 months. When I was hired we were a team of 3. The 3rd member of our team got terminated due to poor performance a while back. In the meantime the company put a hold on new hires and we couldn’t hire to fill that role. Now my manager quit and it’s just me. I was told I wouldn’t have to do her job. I work for a global company so someone else from the HR Global team would step in to help. Well, I had a meeting with said person and I do not feel confident. This person is unfamiliar with current practices/procedures, employees and everything else in the US. She also said sorry I can’t really share in the workload but if you have a problem or anything gets too complicated let me know. I am taking over a big chunk of all pressing matters that were previously part of my manager’s job. She quit during a lay off process, a payroll provider transition, a week away from OE. This week I worked long into the night every day and have so many meetings and pressing issues don’t have time to even have lunch. I feel like this is not doable or sustainable. Im getting emails left and right of hey this wasn’t done and this needs attention and everything is urgent. This is bleeding into my personal life in a way I’m not happy with. Im looking for alternatives. I was told a replacement would be looked for my boss but I know it doesn’t happen overnight so do you think in the meantime do I have grounds to ask for a raise at least? How would you approach it? Also wanted to probably ask for a change in my job title to HR Generalist. Please let me know what you think. Thanks!