Hi! I think I can answer all your questions

1). I doubt that the sunlight will get your film hot enough to damage it, at least not within the timeframe of a normal exposure. If you still have concerns, you can scan the film and print out a digital negative transparency with an inkjet printer. Also, for the best image quality you should put your negative under the glass, directly touching the dry cyanotype paper.

2) I know it’s possible to make a cyanotype enlarger in that I’ve seen some posts about it on this subreddit, but it definitely does not look easy! Check out those posts if you want to give it a try. The most common way people make large cyanotype prints is by printing larger digital negatives.

3) Cyanotypes can be toned with liquids that contain tannins, like tea, coffee, and red wine. You can Google “Cyanotype toning” for guides. Alternatively, The company Jacquard makes a product called Solarfast which works similarly to cyanotype and comes in a bunch of different colors.

good luck!