Ldij is a tax professional. You, by your own admission, at best dabble.
a) OP wife is proposing an irrevocable trust.
b) The life insurance is only paid out after OP dies, so while OP is alive, the "taxation of life insurance" is not a concern.
Yes, good estate planning takes taxes into consideration. However, your concerns for the hypothetic adult children seem a bit overblown.
The simple answer to OP's question is: no, you don't have to agree to everything your stbx asks for. Whether a judge would order these things depends largely on a particular cases circumstances. In many cases it would be unlikely, as the modern thinking is that a woman should be expected to stand on her own two feet.
However, there are exceptions. If OP has not already retained an atty, an initial consultation would be worthwhile.