Macbook air 2019 on Sonoma - running slow, battery dying fast, overheats quick

I'm going to repeat. some of the good advice you've already been given in this thread: First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).  

Additionally, a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

So uninstall the Symantec software and all supporting files according to the developer's instructions. You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For the Symantec software you'd do the following search(es): 

1 - Name contains symantec

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

Also as has already been pointed out your free space is getting down to where it could be dangerous to the health of your Mac. Updates and upgrades often require a minimum of 50 GB to be able to be installed. Also it's often recommended to maintain a minimum of 80-100 GB of free spacer to facilitate optimal system and application performance. Since you have a minimal internal sized boot drive you might consider using the 500GB, 1 TB or 2TB OWC Envoy Pro mini with your laptop to house and run your Photos, Movies and Music libraries plus any large, seldom used other files. It would be easy to carry with the MBA and free up considerable space on your boot drive.

Just some food for thought.

The first thing I'd do is uninstalling the Symantec "security" software.

All this does is waste system resources for no benefit.

I have to wonder if the OneDrive software, with its file services extension, may be behind the excessive cpu usage by "storage" processes:

 ApplicationsStorageExtension 54.20 % (Apple)
  TrashStorageExtension 36.52 % (Apple)
  Storage 27.50 % (Apple)

  StorageManagementService 21.54 % (Apple)

This is most unusual.

Also, having Chrome and its background "keystone" processes may not help, as they are big resource hogs.

The Internal Drive Capacity of this computer is on the small size - 256 GB Capacity

The report indicates the computer is running out or getting low on Useable Empty Space

The less empty space, the slower the computer will work as it tries to find space to handle all changes to files

This is akin to the times when Apple used to sell the Entry Level 128 GB SSD Drives, which should have never been made available IMHO

Unfortunately, the users' needs for Storage Space may have grown since the time it was originally purchased 

The implications being, that on your next purchase

Spend the Extra Money Up Front on a larger Drive Capacity Drive and add more RAM

This may just Future Proof the computer for your growing needs 

Take into account, that after the release of macOS 26 Tahoe, sometime later this year

Support for newer versions of macOS will exclude Intel Computers from qualifying anything newer

And turn off the MalwareBytes real time protection. There is no reason to have MalwareBytes running all the time.