Good morning, and welcome!
1. Yes, 10-12 months seems to be about average right now for Kingston. As far as I know most of the applicants on here have been from Jamaica though, not the Bahamas so I'm not sure if your timeline will be same or not but hopefully it should still be in that range!
2. Yes, Kingston seems to do the processing for the Bahamas
3. If you send in a complete and thorough application with lots of proof of your relationship, and there has not been any previous sponsorships, denied or overstayed visas, or major red flags then you probably won't have to worry about going to Jamaica for an interview. Also keep in mind that if you are not married to your sponsor then you will need to send in a lot of proof of the two of you living together in a marriage like relationship, as they tend to be a bit harder on common law applications than they are on spousal ones. Every case is different and the possibility is always there for an interview, but the majority of people seem to have them waived. If you check out the spreadsheet link under ShortyP's signature you can take a look at the processing times over the last few years and you can see how many have had interviews
4. I don't think so. I believe those are both only relevant for inland applications. If you apply outland you can still be living and working in Canada if you have current visas to do so, but if those visas expire before your application has been approved and finalized you would have to go back to the Bahamas to wait out the rest of the process.
Best of luck, and keep us posted!