I did switch back to mvk format for the recording. Is there a way for it to automatically convert to mp4 once its done?
Yes, 'remux'ing as already mentioned to you is the term for changing the video wrapper from MKV to MP4.
Record to MKV, auto-remux once recording is completed, to change file over to MP4. On my OBS v26.1.1, when I remux, I end up with both MKV and MP4 file. I delete teh MKV, and wait for the MP4 to sync to our cloud backup after service is over. The following week, I move the video recording of the service to a HDD for archiving
lowering bitrate means that is all the upload bandwidth you have available. and that is a very small bitrate. Are you remote with a poor DSL connection, or using Cellular?
For our church livestream to FB at 720p, on a DSL line line, I'm using 5000 bitrate. When COVID-19 first hit, I had to use lower than that, but incumbent phone provider upped bandwidth after a few months to 10Mb/s, so I'm safe at a 5Kbps bitrate. One thing a lot of non-technical folks at churches fail to account for is what else is utilizing the local Internet connection (it isn't unlimited). For example, can parishner's use WiFi? are front/back office computers left connected? etc. All can interfere if you have limited upstream bandwidth (the usual case). If network congestion is a problem (ie you have 5Mb/s upload bandwidth, but others are using almost 4Mb/s of that), your options are kicking the other devices off the network, or setting up a quality of service (QoS) control (at network/router level) to guarantee bandwidth for streaming PC. Unfortunately, most folks haven't the slightest idea how to do that, and often don't have the right hardware to do so. There are free software options, but requires non-trivial technical skill to setup and operate. Sorry, but this stuff does get technical, so beware anyone offering an "Easy" button answer [other than a significant Internet connection upgrade, which might be overkill??].