Why Tor?  Why not rent a cheap VPS and run bitcoind (without the wallet)?

Use a VPN to send transactions from your place. Use the bitcoind RPC as the public interface.

If the transaction is signed then there is no reason to encrypt... it will be public anyway.

If you insist on Tor, rent a cheap VPS. Install the Tor hidden service software and configure the ssh (port 22) interface. Use iptables to close all inbound ports. At your end, get a copy of Tails, connect to the .onion address using ssh, and run bitcoind. Use the bitcoind CLI to send commands.