How to pass User to Push notifications

I've used following article to create Business process to send push notifications:
https://academy.creatio.com/docs/8.x/no-code-customization/bpm-tools/bpm-process-examples/set-up-push-notifications-for-mobile-users

Goal of Business process is to send Push notifications to mobile app about calendar Activities for Owners:

1. Run every 15 minutes (don't know if we can use some Signals based on Activitiy Start time, so decided to run every 15 minutes and check for Activities within next 15 minutes, which is also fine for us)
2. So next setting Start and End dates within next 15 minutes interval

3. Then Read Activitiy records (collection)

   

    

4. and then Send push notification
    

   

5. Issue is than I cannot pass Recepient User, as Owner of activity is Contact, but User is expected

So looking for your help:
1) How to pass respective User for collection of records?

Owner is not available for selection

2) Is it possible to send to multiple users (dynamically defined Owner from Read Collection and static Manager defined manually in Business Process)?

3) How to pass Lead_Name (text) or Lead_Status (lookup) to "Push notification text", instead of Lead_ID? ( I know how to handle this with Read single first record, to Read Lead Data and filter by Lead ID, but don't know how to handle such cases for Collection of records)

Huge thanks,

Leo