Yuh cld setups til yuh fall asleep. 
I said NATIONAL TEAM PLAYERS, not just Trinidad and Tobago. Imho all national athletes, should not be compensated to represent their country unless they win a tournament. How about that... These players earn their livelihood playing at their respective club...that is common sense. But I cld see how "that not making any sense," to some people in here.
So there is this saying practice what yuh preach...if I was a national team player, I eh want no pay unless my team qualify for a big tournament, or win a tournament...
The administration should however, provide the absolute best in terms of insurance, accommodations and preparations.
Yuh stuepsinnn still
Noble idea but what happens in the case of career ending injury early in career while representing your country. Who decides how much of a players potential could have been realized and what they will be compensated. What if that system was in place and a player like Joevin or even Molino got injured before MLS moves? Now all of a sudden you have a players earning potential limited while performing in his professional capacity representing the nation. What do they get? Are they gonna be taken care of for life? Based on the chump change they was making in their respective tiers before ascending to the heights they've achieved? That whole play for free idea is very much flawed, especially when there are profits being generated from the sport. So when Brazil or Mexico and all selling out stadiums all over, the FA keep the money and players get squat because is not a major tournament?
To answer your questions:
1- what happens if they get a career ending injury?
Their career is over---period. Any injury like that can occur at club or national duty. Don't matter where, career ending is career ending.
2- player like joevin and Molino get hurt before mls move?
If these players just relied on national team playing time to support their livelihood, they wouldn't be able to afford even buying food, yet alone pay a mortgage or rent...how many times are they required to suit up in colors annually...thus being a professional footballer, at a club level affords them a decent to great quality of life.
3- Brazil, Mexico, England, Germany, Spain, Argentina, all those big countries and big teams?
All their players I am sure are playing professionally in leagues across the world. Their money to support their lifestyle isn't coming from ONLY WHEN THEY DON THEIR NATIONAL COLORS. It just wouldn't be enough to support a decent quality of life.
A point I'd like to make as well...I'm not 100 percent sure, but ent to secure a overseas contract a tentative player must have been capped by the national team? If this is true, then, that in itself pays to be a NT player.