I also experienced similar side effects when taking too much nicotine. Personally, I've only experimented with it maybe 2 times. I couldn't stand the icy hot burning in the throat. As for benefits, I did get some positive effects on mood, focus, and a bit on anhedonia.
I'm not sure if this is true, but I vaguely remember reading that both agonism and antagonism of the nicotinic acetylcholine receptors upregulates them. However, I don't think people report more benefits from chronic dosing so it's odd in this regard. Perhaps some downstream mechanism gets desensitized?
Regarding safety, it's difficult finding literature that only takes into account pure nicotine and is not confounded with smoking or even vaping. Apparently it has negative health effects according to this review:
Nicotine poses several health hazards. There is an increased risk of cardiovascular, respiratory, gastrointestinal disorders. There is decreased immune response and it also poses ill impacts on the reproductive health. It affects the cell proliferation, oxidative stress, apoptosis, DNA mutation by various mechanisms which leads to cancer. It also affects the tumor proliferation and metastasis and causes resistance to chemo and radio therapeutic agents.
Honestly, I have no idea if it's safe or not. But the harmful effects listed in that article seem, I don't know, exaggerated? Like what is the mechanism of action behind the increased cardiovascular disorders? Is it the drug itself or is it through a downstream mechanism? If it's the latter, wouldn't simply increasing acetylcholine levels also have those negative effects?
Pretty much all those harmful effects come from smoking and I find it hard to believe nicotine alone can cause them.
Also, is nicotine gum expensive in your area? I got mine for free from a stop smoking sample even though I don't smoke lol. It's the brand name Nicorette and very expensive to take on a regular basis. It also tastes rather bad.