With big data usage or other scientific applications leveraging more and more on computing power, requirements for high capacity instances has become a common thread amongst feature request. Therefore, 2 new instance profiles are now available with up to 128GB RAM at Exoscale with evocative...
Have you considered S3 object storage for your use case? If you are accessing this with SSHFS, via a Fuse layer them maybe a direct S3 connection or through s3fs might be more adequate. Furthermore, the cost of Object Storage and the reliability is better than plain VPS storage.
Automated or not, free or not, a CA is all about trust and this is relative to everyone's environment. StartSSL presumably linked to Chinese government (not my statement) https://pierrekim.github.io/blog/2016-02-16-why-i-stopped-using-startssl-because-of-qihoo-360.html will be ok for some but...
Off course Cloudflare and Route53 are good providers but I was amazed that DnSimple did not get quoted. It is a rather effective service and like the name suggest simple and with nice documentation.
Bottom line, my answer is use a provider, self hosting DNS can bite very hard if you do not...