Is my Tor bitcoind node seen by new normal nodes?
Are new nodes able to see me right from the bat even if my 8333 port is only open using a .onion ip address?
  Unfortunately I can't open port 8333 because I'm behind a firewall and my ISP charges for a public IP address.


No... Onion sees onion, clearnet sees clearnet.  Your firewall is keeping you off of clearnet.


  If I want to set up an electrum server (electrumx) using .onion address will it be easy for normal electrum wallets to connect to my machine?


Yes, just tell your users to follow this:


Using Electrum Through Tor