How do you ensure that coins sent to you in a previous mixing will not return to the user at a later mixing?
Also, as you are providing letter of guarantee, use of CDN would not allow MITM. Without using CDN, you are just exposing your IP, i.e. 46.17.96.4, open for DDOS.
It's the other way around...
A CDN is just a content delivery network. It won't protect you against DDOS attacks.
I do know one CDN that's giving away proxy functionality for free... And because they act as a proxy, they also mitigate DDOS attacks to a certain point. However, this CDN DOES act like a MITM. I stay away from any mixer that uses this CDN, since they'll decrypt any data exchanged between me and the mixer and they'll be able to store the unencrypted data in a US based server farm.
I've actually written a complete thread about this in the past:
https://bitcointalk.org/index.php?topic=5247838What the OP is doing is the best possible scenario...
BTW: there are other, better, more superior ways of dealing with a DDOS attack. If you're running an online service, and you need privacy for your users, you should stay away from cloudflare...