I am not a professional or big name in any sense, but hope this helps some.
Make a list of all the big name companies or companies in general you want to be hired to. See what the overall type of games they make are, generally big names have a major demographics and a minor demographic targets. Sometimes the big names also have smaller teams that work on niche games. Make sure the company is working on game types you are looking to work on. Build games/prototypes similar to that.
Using 3d assets that other people made to demo your programming skills is perfectly fine IMO. Mainly because that’s what big companies do, nearly all of the big names buy assets made by other companies that specialize in 3d materials, models, animations, and etc, to combine with the assets they made internally.They re-use their old code as well(Assassin’s creed 1-X/Far Cry 1-X/DarkSouls1-X), similar to the templates we find on the UE4 marketplace.
Start communicating with these companies, the big names have tons of staff and can be quite helpful with aspiring candidates looking for work. Sometimes a quick call to their hiring department to look into what job types are heavily in demand before taking classes is useful. Even asking if you can send in a prototype you have to a hiring manager for evaluation on whether or not you should apply for a programming job and learn more. If you are polite, kind, courteous, and determined, they will remember your name as well when it comes time to look at applications.
Anecdotal Experience: A few friends of mine did the above paragraph in different industries, they contacted the company, Asked them about all the job types in demand, told them they would be trying to work there because they did research and found out it was the place they wanted to be. Every month they contacted them again and told them of how they updated their skills that month to be more inline with the job type. They got the job in roughly 3 months per person, to be fair they already qualified and were only adding on extra qualifications each month. Also this can probably be annoying, so take it with a grain of salt, but showing dedication, effort and consistency with results is a big win in business.