This is regarding the concerns raised in the first post:

- Electrum downloads block headers from multiple servers to prevent any one server from tricking you.

- What you're calling a gateway is actually a proxy. There is one built into tails called tor proxy which routes your electrum connections over the high anonymity tor network. The Electrum that comes with tails is pre-configured to use that. If you install an updated version on Tails you can configure it to use tor proxy too (i believe you have to use tor proxy on tails). Go to tools > network > connection tab, check ssl, choose socks 5 as the proxy, enter localhost as the host and 9050 as the port.