In answer to your original question about backcountry ranger jobs, first, check out usajobs.gov, which lists all of the available jobs for park service and forest service (set up an account and an advanced search to find what you're interested in). might be a little late to get a seasonal job, but I've still seen some openings. doesn't hurt to apply.
These jobs are fairly competitive. it's easier to get a low-level job within the park and work your way up, or a job on trail crew rather than wilderness ranger type. Also, experience helps. The people I know who are backcountry interpretive rangers at Yosemite and at Mt. Adams (seasonal, but have returned year after year) both worked for various non-profit conservation corps leading crews. Gained trail/conservation experience, as well as management/leadership experience. Working at these types of organizations also helps with networking and getting an "in" for a more competitive job. For example, CCC does work for Yosemite/Kings Canyon. Hit it off with the Park service contact, and it's easier to get hired there the next year. And corps hire a large number of seasonal field staff every year, easier to get started there than with the FS or Park Service.
Also, NOLS and outward bound offer leadership courses, more for outdoor guide type positions. However, these programs cost money, and I feel like you can get similar experience elsewhere while getting paid. Though if you're interested in outdoor work, do check out a Wilderness First Aid Course (minimum), or if you're really committed to working outdoors and have some time, take a Wilderness First Responder course. The Wilderness Medicine Institute through NOLS has one of the most recognized courses. Some corps like CREC also offer WFA training as part of the program.
I worked seasonally for years and loved it - some of the best experiences of my life. Definitely some trade offs compared to an office job - the seasonal nature of the job, low pay, not a lot of time at home, hard work - but if you don't mind that, then you can have some amazing backcountry experiences while getting paid for it.