I can't see any reason for the marinating itself to make any difference. If it's safe to leave the (un-marinated) meat in the same conditions for the same length of time, then it's safe to marinate it for that long.
Five days in the refrigerator is definitely stretching it for chicken - usually no more than a few days is recommended, and that's assuming it was fresh when you bought it (not a day before the sell-by date). Even if it's safe, it's not going to be very good. I've accidentally left raw chicken in the refrigerator and forgotten about it before, and it started to smell "off" after about 4 days. I hate to say it, but I wouldn't use it at this point.
As for the steak, you're probably okay, because you only have surface bacteria, but I would cook it well and right away. Again, most cooks I know will recommend no more than a few days in the fridge.
P.S. I've heard people say that weak acids such as lime juice "preserve" the meat, but never from a reliable source; even if it worked, every marinade is different and it would be nearly impossible to predict the exact amount of time it preserves for. You have no idea how much bacteria existed at the outset, and even if the marinade somehow helped to inhibit growth of new bacteria, the "spoiled-ness" of raw meat doesn't come from the bacteria itself but from the toxins they leave behind. It's not a requirement for the bacteria to multiply in order for the food to spoil, if enough existed in the first place.
Unless somebody has it on good authority that marinating makes any significant difference, I refuse to put any stock in that bit of folk wisdom and recommend that others be equally skeptical.
Not sure if there is a correct way. It's basically skewered hunks of meat on a wood fired BBQ
You can do your own Churrasqueira by using a Weber "kettle" style BBQ or a B.D.S. (Big Drum Smoker). Use long steel skewers (or swords!) for your meat and BBQ away
Thick steaks of beef and lamb work well. Also try chicken drumsticks and some small Chorizo (spicy sausage)
Don't marinate the meat, but toss some coarse salt onto the meat surface before and during cooking. Don't go crazy with it, but it seems to absorb the roasting flavours and really boost the taste
Use a smoky fire, if your wood won't smoke add some fresh wood or herbs that do. Try lavender bush (wood and flower), grape vine or kiwifruit vine cuttings, or any other fresh cut aromatic wood
Watch the amount of fat dripping onto the hot coals; too much will make the meat taste bad. Shield the coals as required or trim off large chunks of fat
There is no need for motorised skewers that takes the fun out of it. Occasionally turn the meat by hand while enjoying your favourite beverage, and "chewing the fat" with a friend
Serve by taking a skewer to the diners plate, and hold skewer nearly vertically above plate. Use an extra sharp carving knife and slice onto the plate with a downwards cut so juices and other slicing splatter goes onto the plate and not onto the diners
If you are having a Churrasco party, give each diner a flippable symbol (e.g. red/green) to indicate to the server (probably you) "GIVE ME MORE!", or "I am stuffed". Serve a round of each meat as their outer layer becomes done
Coolest Churrasco cooker I could find
The rails on the top are what the skewers rest on
Following the car theme, some more cool Churrasco cookers here http://autozine.com.br/inusitados/churrasqueiras-automotivas
Best Answer
Be sure to look at this related question too: How does velveting work?
Serious Eats just kind of took this on. They added some nice flavor to the velveting marinade, and then sauced the chunks after cooking. Some kind of adaptation of that concept would probably work well for you.
I have done some small experimentation with adding flavors to the egg/cornstarch marinade, and so far I haven't had any problem. As long as you've got enough egg white and cornstarch to make a light batter, you can add other things for flavor. BTW, the flavor of the velveting recipe in the question I linked to is lovely.