1) Just to be clear you're asking if its possible to send $15 to 10 addresses right? if it is, then yes you can combine them all into one transaction to reduce the fees although i can't give you even a rough estimate as miner fees is decided on how big a transaction is--size but it should be lower compared to sending them one by one.
2). Blockchain.info has already disabled this feature however there are alternatives which is much better imo such as
Electrum, It is a lightweight wallet which means you don't have to download the whole blockchain. There is a
pay to many option on
Tools as well as a preview button to give you an idea how big your transaction will be.
For the fees, always enable
dynamic fees on Tools --> Preferences --> Fees and
Replace by Fee option should be
always so you can add fees anytime.
If you want more info, Here is a great guide for fee estimation
https://bitcoinfees.21.co/ also check if there are many unconfirmed transactions on the mempool
https://blockchain.info/unconfirmed-transactions