Is home financing with 410K realistic and feasible for us?

That is definitely not the case.
The disability insurance pays out in the event of permanent inability to work in the profession. In practice, this means a prognosis of at least 6 months of illness/accident-related absence.

Also, the theory of insuring 2/3 of the net income because 1/3 would come from the state is nonsense. Occupational disability != incapacity to work.
Furthermore, the disability insurance is fully offset against other social benefits to be paid (Hartz 4, housing allowance, etc.).
So if someone insures €1000 for occupational disability, after the insured event they are not significantly better off than someone living on social benefits. Only the insured person has paid a lot for it beforehand.

Disability insurance can make sense if properly designed, but in many cases it only benefits the insurance companies.

Your last sentence applies to ALL insurances in this world and therefore does not need special mention.
Of course, it is about the "not many" cases, where lightning strikes and a person's life experiences a drastic change. This is logically always the smallest portion of the insured, but if you have been struck by lightning, it makes a difference whether you had occupational disability insurance or not.

And the recommendation of 2/3 is of course not nonsense, but an approach to balance coverage and contribution. I am fully aware that occupational disability is not incapacity to work, but with occupational disability I can possibly and am especially allowed to earn something on the side, a simple home job or the like, which fills the last third to a certain extent.
If I can no longer do that, the probability that I am incapacitated to work is enormous. Then the state steps in and I close the gap to net income again.

Again, whoever does not insure themselves against existentially threatening "lightning strikes" may do so gladly, but I have zero understanding for that.

Private liability insurance ---> approx. €70 / year
Occupational disability insurance ---> approx. €50-70 / month (if you start "early")
Household insurance --> approx. €300-400 / year

...and I have insured the existentially threatening risks. Everyone can decide for themselves whether it is worth it to them.

P.S. For the Germans’ favorite piece of metal (car), one gladly pays for fully comprehensive insurance, which as a young guy easily costs €50 more per month. Plus the oil, the good stuff... and the regular washing... but one does not insure one's body, which supports it all, because fifty euros is too expensive. I do not have to understand that.

Unfortunately, I can only press the thumbs up once

Your last sentence applies to ALL insurance policies in the world and therefore requires no special mention.

I basically agree with you that disability insurance can be a very sensible policy. But my last sentence especially requires special mention when it comes to disability insurance. With, for example, personal liability insurance, you can't go too wrong, as each sufficiently covers the basic risk. But with disability insurances, there are loads of practically pointless policies around because people simply insure too little, have an abstract referral in the contract, or fail to see other pitfalls. Many have insured amounts of only 1000-1500€. That does little to nothing and still costs serious money. And it is also true that the claim in disability insurance, unlike with personal liability insurance, depends on many subjective factors. One doctor says this, another says that. Not infrequently, there is even a court case before the benefit is paid, which should not be ignored. I am not saying that people who live off their labor should not take out disability insurance, but that they should understand both the risk and the product beforehand. Personally, by the way, I consciously bear my own risk, even though you have zero understanding for that.