1. Unfortunately, I'm not able to reproduce the first issue. In Angular, it's important to remember that the expanded/collapsed state is stored in the data source. If you load the Gantt chart tasks using the config (and not using the direct API), you need to be careful with changing the task properties (making a change to the data source requests an update of the Gantt chart).
If this doesn't help and you still see the problem, can you try to create a sample project that reproduces the issue (you can use the UI Builder to generate a blank project: https://builder.daypilot.org).
2. The task (and row) height is set using taskHeight property:
https://api.daypilot.org/daypilot-gantt-taskheight/