1.amazonaws doesnt provide dns service?
2.i can only assign static ip through ec2 so the only way to assign domain name is to use third party dns service? which do you all recommend? i need one that able to add SRV
That's correct. Amazon does not provide DNS service so you need to use a third-party provider.
I don't have enough experience to recommend a particular provider, but I have heard of others using DynDNS, and it appears to support SRV records: