short answer - Time for a new computer. sorry
longer answer
real-time video encoding is VERY computationally demanding.
You have an 11 (soon to be 12) generation old CPU, trying to do 60fps.. with a downscale filter that is more CPU intensive.
I recommend monitoring hardware resource (CPU, GPU, RAM, Disk I/O, etc) utilization [for ex. using Task manager’s Performance tab and/or Resource Monitor] to see if your system is being maxed out with your settings
https://obsproject.com/wiki/General-Performance-and-Encoding-Issues and
https://obsproject.com/wiki/GPU-overload-issues
I tried to stream with an Intel i5-6300HQ (2.3GHz 4c/4t circa Fall 2015), 8GB RAM, SATA SSD Win 10 Home edition, Nvidia GeForce GTX 960M and failed as the PC wasn't up to the task (no gaming, just alternating between USB webcam and simple pre-recorded videos, alongside a PPTx slide show window capture, streaming at 720p 30fps with no OBS effects/filters). I’ve learned a lot more about OBS since then, and I might be able to just squeak it out, but wasn’t worth it
So 4 generations older CPU ... uh, be careful with expectations. The GPU helps with encoding offload, but I still suspect your CPU is pegged at 100% for extended periods of time and that is your problem. and/or you have a HDD instead of SSD, and disk I/O (or other hardware resource) bottlenecks
