Lag in Sims 4 increasing over time

My game, it lags. It lags so much I can't play easily. It lags from the moment I open a save, so I'm just building, hoping with each patch the issue will resolve. But I think it's not you, it's me. It's time to ask for help.

I'm playing on PC/Win11 via Steam. The game and graphics drivers are all up to date. I don't use mods or CC in my gameplay, but I did download MCCC and a mod to slow down game time on a different save to try to troubleshoot, but honestly just felt out of my depth, so they were gone again within the hour. I usually get Last Exception when I load a save. They're not exactly the same every time, but I've attached the latest. Attached dxdiag also.

My legacy saves played pretty much flawlessly until around the patch on 28th May 2024. I remember reading about reducing lag on the laundry list and then, Boom! It arrived!

It initally manifested when moving items in live mode, particularly when trying to drag into or from inventory. The item sticks to the cursor, the green box around my Sims' pictures on the bottom left stays lit, and I'd hear the 'placed' sfx a few times, before eventually moving as directed or timing out.

Next, my main household Sims stood around, looking like they were doing nothing, more often and for longer. It took longer and longer for their assigned or autonomous tasks to drop into active position in the queue, even if there weren't any visible current tasks awaiting completion.

Gradually, this has become worse and live mode play is a challenge. Initially it didn't seem to affect other households as much, but by August it was clearly visible. In smaller empty-nest households it isn't quite as bad, but the same problems occur. Still, a household of four Sims and a cat isn't excessive, is it?

By September, the game was completely unplayable, regardless of the household.  As things are now, items moved in live mode are going to be stuck on the cursor for some time. Notifications, actions, and their effects appear to sequence incorrectly. A notification can tell me that a Sim has gone to work, but he appears to be in bed still sleeping, and his icon on the bottom left can show either state. I'm careful not to queue more than two tasks at a time, but they are often dropped or time out, and all the SIms on a lot (including townies) frequently autonomously reset (and stand with their arms out for a few minutes). Basically, I'm pausing the game, waiting for a task to drop, unpausing, watching half the task complete, pausing again, unpausing to check progress or waiting for a notification, and repeating. If I choose not to pause, very little will happen in a Sim day beyond going to the toilet and getting leftovers from the fridge. Background animations and audio aren't affected, and Needs generally degrade at a normal rate, even though eating breakfast can take hours! I can still move the camera and switch to build mode or manage worlds.  When entering build mode from the home lot, paintings and collectibles in particular sometimes become invisible after moving or placing, and the placing of household inventory in build mode can become sluggish (build mode from manage worlds is generally fine).

Looking at the size of my save files - they're huge at about 125mb. I'm only on generation 3! I don't use CC and although I have a couple of large builds, I don't think they're bonkers. Is it a memory issue? How do I diagnose that? Could my save have become bloated with something?

Other things I've tried:

• I toggled dx11 on and off. Frame rates were generally higher, but it still lagged.
• Read and deleted the neighbourhood stories, and tried the 'open game options for no reason' fix. It buys the game more time, but doesn't seem to solve anything by itself.
• Moved sibling households from 'My households'. Deleted sibling households altogether. Deleted lots of townies from 'Other Households'
• Stopped playing rotationally. Rotated more frequently.
• Limited frame rates (the game basically ignores it, doesn't it?)
• Deleted library items, turned off optional game settings (lifestyles, neighbourhood stories etc)
• Reduced the number of activities available to my Sims on their home lots. I ripped out their home gym! They were not happy about it.
• I (reluctantly) rehomed their cat! Thankfully it made no difference, so I moved him back in again. Welcome home, Mayor Whiskers!
• Ripped out plants (planted, build mode and debug types). 
• Replaced appliances for no reason.
• Validated files, repaired the game and performed factory reset. 
• Deleted photographs (ouch) and sold all unique paintings.
• Closed the EA background using Task Manager. Not sure if very slight improvement or just placebo effect.
• Same potential placebo effect when playing offline. Either way, not enough to make the game playable.
• Playing the save(s) on another PC. Same issues, also with last exception on load.
• Deleted lots of prior save files and other things just to make even more space available on my HD.

Just in case it's relevant, packs installed since the issue manifested:

Lovestruck (27 Jul); Spa Day (3 Jul); Dream Home Dec (17 Jun); Jungle Adventure (17 Jun); Laundry Day (17 Jun); Tiny Living (17 Jun ); Cosy Bistro (30 May); Riviera Retreat (30 May ); Courtyard Oasis (20 May); Toddler Stuff (20 May).

Prior Installations: For Rent, Book Nook, Island Living, Incheon, Knitting, Bowling, Industrial Loft, Cats & Dogs, Fitness, Get Together, My First Pet, Backyard Stuff, Blooming Rooms, Crystal Creations, Outdoor Retreat, Max Decor, Greenhouse, Snowy Escape, Seasons, Little Campers, Moschino, Parenthood, City Living, Romantic Garden, Growing Together, Holiday freebie pack.

We're not talking about these bugs here, but I currently also have the San Myshuno festival pile up in the district where my Sims are living. The original saves had the 'can't access gallery sims on the cupid app (now resolved, because I went back to a pre-lovestruck save), and I've also had the 'can't overwrite saves' bug, and the bug with travelling to the Get Famous award ceremony.

I love this game, guys. You've created something amazing, where so many of us somehow care about our Sims and intuit different personalities based solely on the way you've coded behaviours. It's special and I think it's fantastic. It just doesn't work right now! Thanks in advance for any insights.

(Edited to delete the cut and paste content I'd edited in earlier as it's attached in a reply below)