Can you help me in getting the information in below scenario.

I need to pass parameters to an action in lightning like opportunity id, account id. where Account Object is a look up in Opportunity. I am getting opportunity record Id but could not able to get the account Id in the controller
 

I have a use case as below:
1. On case insert/update we need to call an API.

Approach I have taken is: I wrote a future method to call API and called the future method in trigger.

Issue: Now our client wants to insert/update cases from batche job which results in error as future method can not be called from Batch.

Alternate I tried is queuable class but that again has a limitation of max 1 call from batch.
Any suggestion how to solve the above problem.