Yevamos 34a - Issur Achilah and Issur Hana'ah

We find in rashi 3 different methods of creating an issur mosif. 1. the cheftzah shel issur becomes assur to more people. 2. the cheftza shel issur becomes more assur i.e. was assur to eat and now becomes assur b'hana'ah. 3. the cheftza shel issur becomes more limited in what you can do with it i.e. assur l'mizbeiach (rashi here considers this mosif, but in shavuos 24b considers this kollel). The commonality of them all is that the cheftzah shel issur becomes more severe in its issur.

2 points:

1. It seems that it is only considered issur mosif if on a practical level the 2nd issur increases severity such as when aishes ach is chal on top of achos isha, the women who is the cheftza of issur becomes assur to more people (all the husbands brothers). This would only apply if he actually has other brothers aside from the one who is married to his wife's sister. Based on this, when we say that nosar is an issur mosif bec. it becomes assur l'mizbeiach, is that only when there is a mizbeiach, but if the mikdash would be destroyed before it becomes nosar, it would not be an issur mosif?

2. Rashi explains that when the issur of hekdesh is chal on the issur of cheilev, it is an issur mosif since the piece of issur now becomes assur b'hana'ah. Why is this called an issur mosif, it is an entirely different type of issur - even if an issur achilas kodshim can't be chal on top of an issur to eat cheilev, if one would eat it he would be in violation of eating cheilev and also benefiting from kodshim (since eating is also a benefit). I found that R' Elchonon (33:7) asks a similar question, but not exactly on this Rashi. R' Elchonon suggests that every issur achila is really a limited issur hana'ah. Therefore, the original issur of cheilev is a limited form of issur hana'ah so that the issur hana'ah of kodshim can't be chal on it (if not for the fact that it is an issur mosif). However, R' Elchonon points out that based on this one can only be chayev for eating when there is a benefit, but if there is no han'ah in the eating he should not be chayev for achila.