The first thing you should do is obtain a copy of your medical results. These are always available to you under the "Access to Information and Privacy Act". See http://www.cic.gc.ca/english/department/atip/requests-personal.asp
for information on how to request copies of those files. Because you are in Canada, there is no fee for submitting such a request.
Presumably, the time for you to challenge CIC's decision has now passed. That is unfortunate because it sounds to me like you could argue against their decision. The key seems to be the job duties described in the HRSDC listing for this NOC (http://www30.hrsdc.gc.ca/NOC/English/NOC/2006/QuickSearch.aspx?val65=6474
). While it does include "babysitters" it also includes "live-in caregiver" with different job requirements.
Thus, key in an application would be to ensure that your job duties correspond with those of the live-in caregiver/nanny class and not the "baby sitter" class. From your description of what you do, it certainly sounds like much more than the "baby sitter". However, you should also request your computer notes from Sydney because that will tell you why they rejected your application - that's the same privacy act request I mentioned earlier.
If the rejection was because the description of what you do was not consistent with the higher skill level classification (Nanny). There are some key differentiating factors, including:
Nannies care for children in the employer's residence and provide for their health and physical and social development. Parent's helpers assist parents with child-care and household duties. Nannies and parent's helpers are employed by private households, where they may also reside.
This sounds much more like what you described - and note that babysitters do not reside with the family. It may also help if you had applicable education, training in addition to your experience in providing such services in the past.
I take it that you did not apply in the live-in caregiver class, because such applications are processed through Vegreville according to http://www.cic.gc.ca/english/information/applications/live-in.asp
and it does not sound like you yet qualify for an application in that class. Still, it is something to keep in mind for the future.
Something else to consider: you may be able to find employment in your other field of expertise. Alberta in particular has a shortage of specific skills and in that case you will find employers more than willing to obtain an LMO, in which case you would have employment in your field that would also allow you to apply in the FSW category.
Now to try and answer your questions:
1, Can Canada Immigration withhold details of my failed medical, without informing me at any time?
No. You must request it, but they cannot generally withhold it from you (there are some instance in which they can, but they don't seem to apply here.)
2, When my 2 year work permit is about to expire, and my application for a further work permit is considered (My sister has assured me that she will require me for at least the next 4 years), will this mystery code for the failed medical rejection come back to haunt me...will i require a further medical?
By the time you get there, let's hope you have found out the issue and resolved it. However, it is a good bet that it might be an issue when it comes time for renewal.
3, My son will be in his final year of High School, and preparing to graduate when the initial 2 year period is up (Feb 2014). Is there a possibility that Immigration could order our removal from the country, if all applications/extensions have failed?
Based upon what you have described, there is no realistic chance you are going to receive a removal order, certainly not in the timeframes you are discussing here. The most you would get is a departure order
and that is rather unusual. If you ignore a departure order for more than 30 days without complying, it converts into a deportation order. A removal order is a step beyond a deportation order and usually involved criminal activity of some sort.
In addition, your son would likely also qualify for a student visa on his own, particularly given the circumstances (family in country, etc.)
4, Without an offer of Arranged Employment for a FSW application (if indeed my current position does not qualify), i am dangerously close to failing to reach the required 67 points. It's all depending on whether my 2 years College/University experience will be treat as such, due to large parts being home learning. The qualifications gained were Certificate in Management (ILM/NEBSM) and the NEBOSH General Certificate (Health & Safety). What are my realistic chances of obtaining PR status?
Have you considered working on your French skills? There are five additional points there, as well (unless you were already counting on those). Again, you may wish to consider working towards qualification of the live-in caregiver class.
5, My son will be 18 in August 2014. If i have not secured PR status by this time, does he have to apply himself, and what chance has he got?
To be honest, he's probably better off simply applying for student status in such an instance, in which case he can stay and attend University in Canada. After completing a 2 year or longer degree program he would qualify for a 3 year open work permit, and after the requisite period of time, he would qualify to apply on his own.
If you apply prior to his 22nd birthday, you could also include him with your application.
6, Will the work i am currently undertaking be considered as experience for a Live-in Caregiver position (rather than my sister simply applying to extend the LMO)?
It certainly would seem so based upon my reading of the program and your description of your job duties, but the only way to ultimately determine if this is the case is to apply and see what CIC decides.
7, Do i have any other options?
I suppose you could always fall in love with a Canadian.
You likely would benefit from finding and working with an experienced Canadian Immigration attorney, someone familiar with live-in caregiver cases in particular (most likely won't.) Indeed, there are fairly recent legal decisions affecting medical issues and live-in caregiver class, whichis yet another reason to find an attorney familiar with such cases.