My guess is that it's one of two things: Its been too cold for them, as you suggest, and they are stressted Those are male flowers you are pinching off, and if thats the case, then the plant is actally normally Are there l'il cukes behind these flowers, or a stem? If it's a stem, those are the males. The pollinate the female flowers which will show up later on in the plants life

Well the brutal answer is 'It's dead'. As to why it's dead it's impossible to tell from the picture. It could be underwaterd, overwatered, overheated, frozen, attacked by a fungus or a combination of several factors. What is the mix it is in and has that pot got any holes for drainage? What do the roots look like? (It won't hurt it to pull it up - it's past any suffering.) October seems a strange time to be starting cucumbers in Canada so my suggestion, harsh though it might appear, is to give up for now. Do some reading over the winter and start again at a more appropriate time.

Putting them outside all depends on your weather but they would have to be hardened off first. All of the plants are very leggy due to stretching too far for too little light. The stems should only be no more than 1/2 that height. Check out the FAQs here on how to grow seedlings indoors. Supplemental lights are required. Window light alone is never sufficient for young seedlings. Cucumbers are best direct seeded in the garden, not grown with transplants. Not only do they not transplant well much of the time but they grow far too fast for most indoor set-ups to cope with them well enough until they can go to the garden. They tend to stunt if transplanted after the 3-4th true leaf develops. Dave. Here is a link that might be useful: Growing from Seed FAQs

There are many possible problems. My first guess from your description of circumstances is salt damage. Salt builds up in soil from fertilizer and other sources, even the water you may use to irrigàte, and cucurbits are more sensitive than most other crops. If you continue to have poor growth after replanting you may need to switch areas or leach out the existing bed.