1. Chances of approval do not rely on whether it is an online or paper application. It's just the same. Just choose the method that is more convenient for you.
2. Proper requirements: 4 months bank statements, bank certificates, certificate of employment, proof of financial assets, etc. He needs to show proof of his ties to his home country/country of residence (difficult because he is a seaman), or proof that he will leave Canada at the end of his visit (e.g. his travel history not related to his work).
3. Time of processing at Manila is about 2 weeks for most applications:
http://www.cic.gc.ca/english/information/times/index.asp
Again, since he is a seaman, there's a chance it might take longer.
In my honest opinion, because your boyfriend is a seaman (the nature of his job makes it likely he will try to find work in Canada), his chances of approval are low.