1. As you were in Canada already - you could have applied via the online application system (http://www.cic.gc.ca/english/e-services/work.asp)
http://www.cic.gc.ca/english/work/apply-who-eligible.asp#inside
I see that based on docs you mentioned here - you were eligible for the online application. The links at the end of the page if you click on the link above lead you to the link to the online application.
Now to answer your question there will be no notification of acceptance like an AOR. The VO will contact you on the next steps (like getting a medical examination etc.) required.
2. You may have a problem if you return to the Philippines as the address in your WP application may be that of your temporary residence in Canada. Please check that. If that is the case, your file may need to be transferred to CEM (Canada Embassy Manila) from Buffalo as then since you have returned to the PH, the VO serving the Philippines is CEM. I suggest you contact the CIC hotline for clarification.
Note this : http://www.cic.gc.ca/english/visit/extend-stay.asp - check this link - typically work permit applications are applied for before coming into Canada.
You have an option of renewing your TRV if you opt to remain in Canada to wait for the results of your WP. Please note the processing times to guide you on the period of waiting for a WP and deciding if you want to renew your TRV. If you want to remain here in Canada to wait for the results of the WP application, and extend your Visitor Record (this allows you to remain in Canada but not re-enter), note that while waiting for the extension, you have 'implied status'. See the link I sent for more information.
3. Have not heard a lot of cases in which the change of conditions from Visitor to Worker happened without the need for the applicant to exit Canada. Most often, they needed to exit and wait for the WP. There are cases wherein you can apply for the WP upon entry - but you don't fall under the category of visa exempt (PH is not visa exempt) .
See the end of this link: http://www.cic.gc.ca/english/work/apply-who-eligible.asp#inside - the section states: Eligibility to apply as you enter Canada
You can apply for a work permit as you enter Canada, but only if you meet the following requirements:
you are temporary resident visa exempt and
your job does not need a labour market opinion from HRSDC (some exceptions apply) or
you hold a labour market opinion from HRSDC.
Note - you need to satisfy the first condition and either of the next two conditions.
Hope this helps