you cannot get a divorce as you are still a phillipines resident in order to get a divorce you have to be a citizen of a foreign country then you can get a divorce and it would be considered a divorce as you have obtained a divorce in your now country of resident, although in the phillipines you would still be "married" but they would recognize your divorce, so in that essesnce conjugal is the way to go please ensure you include proof of genuineness in your application. I wish you the best
no, i've never been a US citizen (and either has my ex) and we divorced through the US (where he is a green card holder)... my divorce is very legal... if you are legally divorced, canada will recognize this... They will not be able to marry in the philippines if/when a divorce is received... which is a different hurdle, but one that can be overcome with a little creativity...
getting a divorce in the US (from outside of the US is possible unless they physically need you to be in court... most times a lawyer can represent you (and i don't believe a judge will dismiss a divorce case because you are not there), if there are custody or financial issues that need to be addressed that you think the ex might put up a big fight for, you may be required to attend session)... my divorce was simple and neither one of us was required to appear...
as far as getting a TRV... I couldn't say.... having a US green card would likely be highly beneficial (do you even need a TRV if your green card is still valid? I'm not sure, i know entering the US, a Canadian PR needs a visa, logic would say that it would work the same way going into Canada, but things defy logic sometimes

)... regardless it's a plus for your case, but nothing is certain
if you do require a TRV, it's best if you have family who can invite you... your boyfriend should try to not use the words girlfriend or fiance if he is the only one that can do it, your chances will greatly decrease if he calls you that as your chances of overstaying are high...
hope that helps some