A very late reply that doubtless will be of no use now, but nevertheless I offer it for edification.

Medical: bandages, scalpel, aspirin, tweezers, adhesive tape.

Of the available items these are the most likely useful for your trek. Snakebite kits are strongly disrecommended as they do no good whatsoever. Morphine has it's own problems and will leave you potentially unable to trek due to it's sedative effects. Take aspirin and suck it up if you wish to live.

The bandages and tape will aid with the inevitable cuts, scrapes, etc, and the tweezers with the thorns that will find their way into your flesh (been there done that in Belize).

General: matches, soap, compass, knife, mosquito net.

Fire is a basic necessity for heat, light and cooking, as well as nighttime safety in the jungle (predators). Soap is your infection control measure for the inevitable wounds. Compass so you can stay on track when you find the inevitable obstacles. The knife is your primary survival tool for building shelter, gathering fuel, cleaning and harvesting food such as may be found, and finally as a last-ditch defense. The mosquito net will make the night more bearable as far as sleep and keep you healthier. You won't make 100 kilometers in a couple of days so plan on staving off possible mosquito-born infection as long as possible.

Ayrman