You're not horrible on camera! You're fine on camera, you just seem slightly uncomfortable which is fairly normal, thats why so many youtubers hide behind that "HI GUYS! SO AND SO HERE, LIKE AND SUBSCRIBE!" stuff. Slightly uncomfortable and genuine > fake and confident any day (to me, at least). If you draw little dots or eyes over the camera lens and look at those like they're eyes it feels more natural and you might come across as more "comfortable", you'll start to forget that its a camera. Once that happens it's noticeable on camera and you'll seem more comfortable (and you wind up with a lot more footage of picking your nose and zoning out lol). Whether consciously or not, staring at the lens you start to think your reflection is goofy looking and make weird face movements to correct what you see in the (heavily distorted) reflection. By not looking at the lens, you circumvent that feedback loop.
Don't look at things as weaknesses, look at them as places you can learn/improve. It's helpful, not critical!
With the mixing stuff, I only notice because I am a bigtime audio nerd - but if you want to aim for great audio, always preview your mixing with a few different audio outputs. I usually use etymotic ER4SR headphones when on the computer - but if I edit/audio master wearing those, people on speakers will find it "muddy" because the ety's provide exemplary separation that most speakers/headphones can't differentiate. If you edit your audio with bose headphones, anyone using clean/reference headphones will find the audio too "sharp". Try headphones, and some speakers, maybe a few different pairs of headphones until you get an idea of the ideal "signature" you need to target. Just because they sound great in one pair of headphones doesn't mean they'll sound great in all of them. Some great open-backed headphones to use for editing stuff on the cheap are Koss KSC75's, they super clean, no boosted bass, and the separation of audio channels is exemplary - and they're dirt cheap (also, if you get some, reply back and let me know what you think about them for the cost!!).
https://www.amazon.com/Koss-KSC75-Portable-Stereophone-Headphones/dp/B0006B486K
Make sure after mastering you test with speakers or some different commodity-headphones, like iphone headphones or something, so you get to hear what 90% of your viewers will hear.
To grow *subscribers*, create a narrative that goes from one video to the next, i.e. start a project in one video, and continue it across a few videos, like.... do your normal videos at 2-3 minutes, but also have a 30-60 second update of your long-term "narrative project" so people who want to see the progress of the narrative project have to keep coming back. Every 5 videos or so, have a longer/bigger update video. Subscribing is the easiest way to keep track of those updates
- the channel "Mighty Car Mods" did this really well with their older videos from a couple years ago, though now they've got that strong "sellout" vibe going (but they're getting paid, so good for them). Occasionally mentioning that people subscribing helps you out, without begging, wouldn't hurt. Give people a reason to come back, rather than just watching the video that they searched for, and maybe one recommended by Youtube. Heck, might not hurt to make a video asking viewers what they'd like to see, and making a few (reasonable) viewer request videos.