Addition of honey and vanilla to cooled wort

Yes to both.

Honey is not all that uncommon in beers, as it is often used to increase the gravity, and/or add a distinct honey flavor to the beer, giving it a mead-hybrid taste. To avoid giving it an overly mead flavor, and adding to your fermentation time (honey is notorious for taking a while to mature in flavor), it's recommended that you use up to 10% of your grain bill (by weight) of honey. If you want to add more more? Whatever blows your hair back.

There's several ways you can add it to your wort. You can dilute it in water to the same original gravity as the rest of the wort, pasteurize it by heating it to at least 176°F/80°C for an hour, cool it, and add it to the batch, or you can simply add it to the cooled wort for an increase in your original gravity. The former method prevents your OG from going up, the latter will increase your OG. A lot of people are advocates for adding it to the wort during high krausen, when the yeast is most active and ready for it. Expect to wait an additional 3-8 weeks for fermentation and aging depending on how much honey you add.

A lot of people have reported greater success using vanilla later in the fermentation and aging rather than earlier. You'll only want to add vanilla extract at bottling. If you are using vanilla beans, you'll want to cut them down the center, scrape out all the goods inside of the been, and chop all of it up very finely. It's best to soak them in vodka for a couple of days, and add to secondary slowly until you reach the flavor profile you're looking for. You can add all of it at once if you're feeling brave, or add half of it, wait a week, sample it, and potentially add the other half if you're dissatisfied with the lack of vanilla flavor.

If you go the extract route, the best way to determine how much extract you would want is to find a good commercial example of a brown ale, pour it into a glass, and slowly add drops of vanilla to it over time, and stir. Determine how many drops it takes to get the right profile you want, and then scale the number of drops up to your full batch size. Add it to your bottling bucket and stir well before bottling off your beer, or add the drops individually to each bottle before capping. Keep in mind extract is powerful stuff, and it is very easy to overdo it.