one person = one language
If you speak both English and Chinese to your son, he might be later confused on what words are from which language.
I would recommend you only speak Chinese to him. For our kids, English is now their strongest language but it was only taught by their 'environment' i.e. kindergarten / school and they started with English only at age 2-3. Now they talk English with each other (before they went through a period in which they talked German or Thai with each other). So you should not underestimate the 'environment language'.
Also, you might consider having some other relatives speaking certain specific languages with your son (e.g. grandparents). This could reinforce their language skills.
Personally, I do not believe that learning languages from TV is effective. Learning languages is about relationships and interaction. I think the 1 hr per day would be better spend on interacting with your son in the respective language, e.g. by playing memory game etc.
Regarding late development of speaking. We did not experience this with our kids. But they might be a bit delayed when learning to read and write because of different phonetic rules of the respective languages.
I was told this by many people but I am not sure why they say this.
My wife and I always spoke a mixture (German/French) together so of course did so also with our kid (plus English/Spanish outside the house). He had no problem, and in school or was quite orthodox in regards to which language to speak with which person. But at home or with relatives and polyglot friends he would switch back and forth. His classmates seemed to be the same.
I have seen my mother, in her 70s, switch mid sentence when arguing with her brother. Then turn and speak to my father in English.
To me, a child learning from listening to the TV is like a form unsupervised learning. It probably helps them build an internal representation of language structure, but doesn't teach them much if anything about proper use of language. If I had to guess, I'd say it is probably mildly helpful when the child is very young (especially if the alternative is silence), but it probably stops providing any value fairly quickly (by about a year of age for the typical child would be my very uneducated guess). At this point, I'm guessing improvements in language facilities probably require focused interaction (supervised learning).
When I was child we had re-transmitted children German tv shows, I could speak German a bit without actually learning it for other sources.
Disclaimer: I'm not from Finland, but had discussion with one of the teacher in there.
[0] http://en.wikipedia.org/wiki/Dubbing_(filmmaking)#Finland
Playing memory game is a good idea, we haven't done too much of that.
I personally was brought up with 3 languages (English, Cantonese and Malay), which would be common if you grew up in a multi-cultural country.. no one ever thinks it's a problem there.
The older kid said her first sentence consisting of three words at 18 months, but the younger kid did not. By that stage, both had a large vocabulary of words to express themselves, and even larger vocabulary of words that they understood.
EDIT: Missed the detail about "since birth". So no, my example does not answer your question, since they were exposed to only one language --- Marathi --- until 18 months.
Key in the early learning stage is the relationship of person to language and to repeat it
one person = one language
Our family conversation is happening in English and that is their native language by a distance. The girls do have daily Chinese afterschool program and with my wife using it daily it kept them very proficient. My German use is limited and I can tell they are getting a little rusty.
I wonder if his confusion over the 3 languages pay the major part for his late speaking abilities, or if he got too much of my left brain genes, or a bit of both. Anyone here with experience teaching their kids 3+ languages since birth? What was their speaking ability like around this age?