To win in (-) point spread bets the team you want to bet on has to win by at least 1 if not it's considered as a loss or a push depending on how many points you take and vice versa for (+) points.
With your bets being -3,-2 and -1 the Jags has to win by at least 4 points for all three bets to win.
If the Jags win by 3, the -2 and -1 win while the -3 will be pushed.
Depends if the market is Asian handicap or European handicap.
On European handicap markets, there is no voided market, so -3 is actually the same as -3.5. Always make sure to double check the rules of this specific market. But most bookies use the Asian handicap on NFL I believe.