greatest, you used a bad example in the gemoro in Rosh Hashono – It talks about a korbon, which was brought voluntarily (lirtzono), and compulsion isn’t poshut at all in that case. You should have brought the gemoro from kesubos pey vav omud beis, where it says “makin oso ad sheteitzeh nafsho” to make him do a mitzvas aseh.
But this is hard to translate into halocho, because we know that malkos were only given during the time of the sanhedrin, and even then, if the person couldn’t withstand all 39, then the number was reduced – with this statement, ad sheteitzeh nafsho, that limit isn’t considered – so a bdieved miderabonon has a harsher punishment than a mideoraiso? No way.
Also, there is an even bigger issue. The gemoro in the first perek of makkos asks the obvious question about eidim zomemim – if its a laav she’ein bo maaseh, eino lokin olov – in this case, as by NOT doing something, there is no maaseh, how can there be a recourse to beating the person, even to death, comparable and even more severe than makkos? Again, and now in this context, Are you prepared to have your son beaten to death if he refuses your compulsion to put on tzitzis? because that is what you are suggesting is OK by quoting the gemoro as you did for applicability today.
Finally, as you should have noticed, both issues in both R’H and kesubos are from braisos, not mishnayos, and thus as you well know don’t have the same status in halocho, even if they do have the strength to make a point in the gemoro.