Welcome to our community and thank you for reaching out to us! I'm glad to help out.
Let's see: regarding where you can get married, you are correct - as your partner is still within his asylum proceedings it is best you get married in Germany. However, it's only possible to marry in Germany with a valid passport.
Our law expert Marcel gave an answer on this thread here that can be helpful:
how can a canadian marry a refugee who is still on process
There are many documents you need to collect as well in order to get married (German bureaucracy). Please have a look at this thread: I'd like to learn more about the marriage procedure in Germany as a refugee
If you follow the link Thorgen posted in his answer, you will get to the Wefugees Blog with a long English explanation on "How to marry" in Germany.
This source might be particularly interesting too, as you are a Non EU-national (it's relating to marrying German citizens, however, it should apply in your case as well):
"If you are a foreign national getting married to a German citizen, it can impact your residence status. If you aren’t living in the country yet, you may need to apply for a special visa. Non EU-nationals cannot enter the country on a visitor visa if they are planning to get married in Germany. The required German visa is usually valid for three to six months."
As for the waiting time, it is hard to say how long it takes, but also talked about in the sources I linked.
You can get married in Nürnberg. Asylum seekers are not allowed to leave the region/ Federal State when a residence regulation ("Wohnsitzauflage") applies. This is the Nürnberg Standesamt website (in German, but you can try a translating program): https://www.nuernberg.de/internet/standesamt/heirat.html
Regarding your last question: His asylum procedure is a different process than your marriage procedure. Once you are married, you can apply for family reunion so he can live with you in Canada (if that is your wish). If he gets a protection status in Germany, on the other hand, he also receives a residence permit, and there are regulations for spouses of residence title holders enabling them to live with them in Germany.
Please note that the information I shared with you stems from my research, I'm not a lawyer. Once you are in Germany, you can also seek help from a legal aid service for refugees/ asylum seekers in Nürnberg. For example, the Refugee Law Clinic Nuremberg: http://www.rlc-erlangen.de/beratung.html
I hope I could answer most of your questions. Feel free to reach out to us again if you need any further assistance, and also have a look at our platform for previously asked questions regarding marrying a refugee in Germany!
All the best, take care,