I think the way you suggested the rates are a bit high you should definitely lower the success rate.
As for the breaking items:
I personally do not prefer it since i have played A LOT of Mmo's where i experienced this function way too much. I have already read some of
the comments here saying that it could lead to being a p2w game. And Yes i have to agree with that many old games i must say here are p2w and this is exactly one of the reasons ( for example Flyff and the common games at that generation ). Of course you can buy them but that would make the game a business thing instead of actually " playing " something to purely have fun and achieve things. In my opinion grinding money and buying an overpriced weapon or the material to use that the weapon does not break is no achievement at all it is just awful to do so.
Many newer games already got rid of this function. There is Blade and Soul which came out recently in Eu/Na and this game is just a hit everyone plays it and everyone enjoys it ( in the most part ) this game also took too many years to finally get released here in EU. Well anyway this game is really good and also doesnt feature breaking items. It has its own unique Weapon Enhancement System which makes it very interesting to play let alone the great combat system.
Please do not get the wrong Idea for me advertising this game i just used it to show a proper example of a succesful game not having the requested function we are discussing here.
Also no breaking weapons are most likely more " Casual Player friendly " and that way more people will be having fun in this game and thats what its all about right? I am sure you get plenty of donations for doing this great work and i also appreciate it so we dont need any further function which could lead into making this game p2w 
So thats what i had to say i hope it helps