Massive gap between 10 and 12

OK so I have a number of problems with the games positioning of players.

First of all when in defence if the ball ends up fairly wide then my 10 and 12 leave a big gap between them that of course makes for an easy break. Is this down to my 10 getting too involved in the breakdown area? If so then would altering ruck aggressiveness change it? I can't think what else would.

Second is there any way to get your 15 to stay in the middle. Again when the ball is out wide he is determined to sit directly behind it, even if that leaves a 50 yard gap between him and the opposite winger.
Hi, same question here. Can't find a way to get my 10 to stay out of breakdowns. 15 does not sweepthe rear properly and when I'm nkt playing at home, 14 keeps moving to the opposite side leaving a huge blind side akmost everytime. Has anyone found a solution for these issues?

Best,

M