That's a lot of gum you chew a day. But definitely still tobacco. You get more microplastic from other source than chewing it, but you get 100% of nicotine from smoking.
Apparently it's not the nicotine that is bad for you but the smoking (snusa, or chicking tobacco under the lip, is not particularly bad, or I'm on old research papers), inhaling smoke is really bad for you though and that is something we really know about.
Also, I guess we would have noticed "gum chewers" dying everywhere like the 2G phone users, or flat earthers going missing when hiking...
If I'm not wrong there are non-plastic based gums available too, sure they are expensive but if you are concerned about mixeopastics you should comcder that option
There is no such thing as 'more deadly'. The adverse effects of smoking to your health are known. The adverse effects of nanoplastics and accompanying compounds are less well known.
If you are concerned with your health than actually be concerned with your health, stop doing unhealthy shit with any frequency. Eat plantbased, exercise, get yourself checked out at a doctor, do a blood test. You know what a healthy lifestyle looks like. Do that.
If that's 10 a day sugar-free gum it will destroy your intestines eventually. If it's sugary it will destroy your teeth. Smoking twice a week is probably even less harm than inhaling cars exhaust on streets everyday.