What is the strength of the seed rated ad? Is it possible to hack the word key?
The seed is 128 bit, so its perfectly fine. Not sure what you mean with hack here, but a brute force attack is not possible no.
Let me rephrase that: Yes a brute force attack is possible, but not feasible.
Using any dictionary wouldnt make any sense, the dictionary used by electrum is known[1]. With 2048 possible words and 12 selected from that list there are 204812 possible seeds, which is actually more than 128 bit (log_2(2048^12) = 132)
[1] https://github.com/spesmilo/electrum/blob/master/lib/wordlist/english.txt