As some things may not be as clear in the rules as one might want. Here are some comments from the GURPS Line Editor who wrote the 4e rules.

Grappling and Knockback
For simplicity's sake:
* If you're knocked back while grappling someone and you'd be strong enough to walk off with your victim (more than twice victim's ST), your victim is treated as something you're carrying and is knocked back with you unless you opt to let go.

* If you're knocked back while grappling someone and you're not strong enough to walk off with your victim (more than twice victim's ST), you're knocked away and the grapple is broken.

* If you're knocked back while someone is grappling you and they're strong enough to walk off with you (more than twice your ST), they may opt to keep you there or let you go.

* If you're knocked back while someone is grappling you and they're not strong enough to walk off with you (more than twice your ST), you're knocked away and the grapple is broken.

In a mutual grapple, check both conditions.

Whether knockback is large enough to send both parties flying is getting too complex for this rules set.

Gather Information
In GURPS, as in real life, there are dozens of ways to get info using one's skills. It's up to the player to propose and the GM to dispose. A few examples:
Administration to glean info from a bureaucrat, either through discussion or by filling out the right forms to request it.

• Area Knowledge to know where people with useful information hang out so that you can bribe, trick, spy on, or otherwise interact with them.
• Carousing to buy a few rounds and get information at a pub or a tavern.
• Current Affairs -- a simple roll will often suffice once you've spent some time catching up on the latest news.
• Fast-Talk to pry information from somebody who knows what you need to know and who shouldn't talk . . . but who is easily bamboozled.
• Intelligence Analysis to discover useful info in the reports of people who use these other skills.
• Interrogation to squeeze information out of somebody you corner or capture.
• Lip Reading, Observation, Shadowing, Stealth, etc., to spy out information the hard way.
• Merchant to buy information legally.
• Politics to glean info from a politician, perhaps by promising cash support or by convincing him that something untoward is going on under his nose and that you can help if he fills you in on a few facts.
• Research to find information in records of some kind.
• Savoir-Faire to glean info from somebody in the relevant social group by convincing him that you're a peer who "needs to know."
• Sex Appeal to get information from a horndog.
• Streetwise, either to find people to bribe, interrogate, and spy on, or simply to walk the streets, make contacts, and hear rumors.

"Information gatherer" is an entire PC profession -- every group needs one. Somebody who's good at that task will have most of the above skills, plus advantages that boost them and/or give reaction bonuses, and probably a decent bankroll.