I ran into this exact issue a while back. My Outlook PST file had grown so large that Outlook kept freezing, taking forever to open, and crashing randomly in the middle of work. I tried a couple of free tools to fix it, but they either failed midway or didn't support files that big.

Eventually I used Shoviv PST Splitter Tool, and it solved the problem pretty quickly. It let me split the oversized PST into smaller files based on size, and everything — folder structure, emails, contacts — stayed intact. No corruption, no missing data. Outlook has been running smoothly ever since.

If anyone's dealing with the same issue, I'd genuinely recommend trying it. It also has a free demo, so you can test it on your file before buying.
Read more: https://www.shoviv.com/blog/how-to-split-pst-file-in-outlook-manually/