1- you can use it immediately or store it. The pH of 5-1-1 is NOT terribly low for most plants.( ~ 5.8 - 6 ?)
2- You can use any granular CRF. I use MG Shake n Feed.

3- I am not well verse about house plants. Check Gritty mix for your application.

I just use 5-1-1 for annuals like tomatoes and peppers. For FL I think you would need more moisture retentions. So yes, more peat moss. I would also try adding DE(floor dry).

I am not sure that original 5-1-1 formula is a good choice for deep south and FL. Wait for more inputs.

Sey