/ Additional capacity for Nordstream II - Germany plans to buy hydrogen from Russia and use NS II for transport
which accounts for less military spending.
As if autocrats ever cared about balance sheets regarding military spending. The economic problems of the last few years have not affected Russian military spending, and if necessary, Putin will introduce welfare cuts and defend them with security needs.
Besides, what you are writing here are short- to midterm concerns. When we think about security, we need to think long-term instead. And it is pretty clear that the USA is losing interest in Europe. Russia is no longer their number one concern, and the threat of China will only grow in the future and likely demand America's full attention. Yeah, selling some gas is nice, but the USA will likely not be in this buisness for very long and even then it hardly justifies the kind of military spending it requires to deter Russia.
The thought that the USA - who are already unhappy with this situation - will be able and willing to guarantee Eastern Europe in say 20-30 years, while possibly also having to defend South Korea and Taiwan is very optimistic indeed. And things went rarely well for Poland when they relied on optismism. Just look at PiS European policies. They thought it was a good idea to rely on the UK, and now they are without any mayor allies in the EU.
Feel free to disagree and present me with your arguments, this is really one subject on which I am very relaxed about since Germany's position is very secure regardless. Though I'd feel very bad about Poland if things went wrong.