On the philosophy of it, you seem to be missing the vital characteristic of things like this, which is that they are
not within our control. Whether Johnson decides or doesn't decide to institute a lockdown in January will be a matter for him, his advisers and the Cabinet (to say nothing of Parliament), and certainly not for Gromit, or anyone else on AB for that matter.
It's the same in everything else in life -- or, put another way, you seem to be mistaking personal certainty for objective certainty. Even if I am personally certain then, as long as it's beyond my control to influence the outcome, of course it would be gambling to put money on it.
As far as I can remember, I have taken up two of your bets in the past. It's worth stressing that on neither occasion did I do so because I was certain about my position. But since it would only lead to a small donation to charity if I lost, I didn't then see it as gambling. People are entitled not to share my perspective on this. This is also the reason that I only play poker with fixed stakes, say a tenner for the evening, which means that really it's just buying an evening's entertainment rather than genuinely betting on anything.
As to your first question -- I point you to rules 1, 7, and 9 in the list of
Site Rules. It's getting spammy to go on and on about offering bets that others aren't interested in, especially when (a) directed towards the same person/people, and (b) when it's coupled with a criticism of their character for not engaging with you.