Can you respond to קדושה if you are not already done with your own ש''ע? I heard that you can if you are past a certain point after שים שלום/שלום רב. I just want to know if that's true and, if so, exactly what point in the ש''ע must you have passed?
Yes, this is true. This refers to after you have said the first "yih'yu l'ratzon" and are now in middle of "elokai n'tzor". Different authorities disagree on how you may interrupt, so here's some sources.
This website says:
"one may answer Amen for Kadish, Kedusha, Barchu (and all the other things permitted Bein HaPerakim of Shema), and according to some Poskim any Amen for any Bracha, as Shemona Esrei is over already."
The newer editions of Siddur Tehilas Hashem have a chart of permitted/prohibited interruptions. It appears that most of the laws are the same as bein haperakim of shema, except for putting on talis and tefillin. It says that:
- you may answer "amen" to birchas hatorah.
- for kaddish, you may answer only "amen yehei sh'mei...." and the last "amen".
- for kedusha, you may answer only the responses of "kadosh", "baruch", and "yimloch".
- for answering modim, you say only the first three words: "modim anachnu lach".
- you may answer barchu.
- you may answer "amen" to "hakel hakadosh", and "shomeya tefillah".
- you may go up for an aliyah, but you should not read along.
- you may say the blessings on lighting and thunder.
- you may not say shema with the minyan, rather you should continue davening but with the tune of shema.
- everything else is not allowed.
Yalkut Yosef vol.1 Hilchot Tefila pg. 176 he says that one should answer "Kadosh" and "Baruch" in the middle of Elokai Nesor as well as the first 5 Amenim of Kadish (the Ben Ish Hai holds that one may even answer Amen DeBerachot. However, Hacham Ovadia I believe writes in Yabia Omer 6:48:4 that one may not do so). However, if one didn't say the first "Yehi Rason" he may not stop for kedusha or kaddish (first 5 Amenim) because it is part of the Tefila.
However, if one already said the second he may answer any davar shebikdusha, including Baruch Hu UBaruch Shemo. (see Yechawe Daat 5:10)