EM warfare questions about German technology

[Incubus]

The German radar sets seem pretty crude compared to what the allies could offer. I had a couple of questions about it-

1.) Somebody mentioned that on US subs, skippers used radar to obtain firing solutions on enemy ships. While this wasn't necessarily done on German U-boats, a thought occurred; you can manually use the radar (there is a tutorial on the wiki page) and, if you are using manual fire control, would it be possible to obtain a firing solution solely from using the radar? With 100% realism, it would be an interesting way to get medium-range shots on ships in bad weather.

1b.) In theory you could also use Sonar to accomplish the same thing, and fire at ships from max launch depth (20m) without ever having to pop up the scope. Only problem is the pinging is a dead giveaway, and I heard that several pings can cause merchants to wise up (not certain on this)

2.) Historically, was it possible for radar sets to 'jam' enemy radars? It would be neat if you could use your own set to jam an enemy's radar- they'd know you were around but wouldn't be able to find your exact position. In bad weather you could then, in theory, sneak around SURFACED. However I know that Germany was slow to pick up on the use of centimeter-band radar, which became the standard for the Allies in WWII.

3.) Were German submarine radio receivers able to intercept enemy communications? It would be fun to hunt enemy merchants by zeroing in on merchant traffic.