Hi,
For L3 I do not recommend to mix with x440 (especially x440 because of their very low L3 capacity). I think I clearly state it above, and your experience proves it.
What I was trying to say in the post above, is that EXOS tries its best. But at the expense of CPU usage and possibly some slow-path... that can be a life saver if you're close to the limit of the lesser one. But no miracle will happen and if too many entries, you're doom.
The x440G1 is hardly a L3 switch imho, you really need to be sure of the (small) size of the network. But EXOS behavior is very interesting with intermediate switches (in a stack) or modules (in a chassis).