No problem.
Yes, enemy sonar gear and skill does improve, as it did in real life, through the war . Will notice as war goes on, especially into 1944 the enemy ASW vessels becomes more difficult. This is due to improved sonar/sound gear being introduced (Type 93-5A and 5P, as well as later the Type3-1A and 1P on certain units. Type3-1A and 1P are the best gear, some of the more main line escorts and DD's get them in 1945. There are also more of them and more convoys and start seeing special built ASW vessels (Kaibokan) such as Type A, B, C, D escort vessels.
TMO simulates the two type of depth charges used by IJN. At start of the war Japanese used Type 95 depth charge from start of the war. In late 1943 they began using Type 2 depth charge...which was heavier i.e. more explosive power, had a faster fall speed, and a hydrostatic exploder which could be set beyond at depths up to 480 feet (Some sources said a later improved exploder could be set up to 600 feet, which I believe is accurate based on patrol reports. Deep diving boats like Balao class coudl go to 600 feet and reported depth charges at that depth, being forced to 650 feet) (Japanese assumed US subs could not dive deeper than their boats at start of the war so their depth charges were designed accordingly, max depth setting was 300 ft for the Type 95 used at opening of the war.
After a idiot congressman returned from a tour of the Pacific Theater, he bragged to US reporters that US subs were safe because Japanese were not setting their depth charges deep enough. Japanese intelligence of course got wind of this, and a improved exploder for Type 95 was introduced in 1943, and US sub losses went up rather suddenly...ten boats or so. Then the Type 2 was introduced and losses continued to climb.
Yes, circle running torpedoes are modeled as are all the torpedo malfunctions. In TMO Update V1.0 they are modeled well and even more so in V2.0. Their improvement follows history. From start of war the MK 14 torpedo will run deeper than set, explode prematurely, and the the contact detonator is faulty, so will get quite a few dud torpedoes. Unlike the Germans, who solved their problems quickly, the US sub captains had to fight with their bureaucracy. The depth control issue was not really solved until early 1943 and some torpedoes still ran deep during the war, but as 10-12 feet in most cases as before.
Magnetic exploders were never really fixed, they were deactivated by Pacific fleet boats in June 1943 and Australia based boats (Different command and Admiral Christie, the Commander, had played a key role in development of the magnetic exploder, so was reluctant to deactivate them) on 20 January 1944.
Dud torpedoes are a issue until early October 1943, when first improved exploders on torpedoes made it into combat.
MK 14 torpedo (steam) does always run a risk of a circle run, but its higher in early war. At least one submarine (Tuilibee) is known to have been lost to a MK 14 circle run (Feb 1944 off Palau) . Grunion (lost in Aleutian Islands) was most likely sunk by a circle run MK 14 as well.
MK 18 electric torpedo had issues as well when introduced. MK 18-1 entered service in June 1943 (does in the sim as well, at a cost ) . While did not suffer the detonator problems of the MK 14, since it had the MK 8 contact only exploder, which was not magnetic and had a different impact exploder. However, first batches of MK 18's tended to run deeper than set, had battery issues preventing them from reaching full 29 knots and thus missing target, gyro issues, and a nasty tendency to circle run, more than the MK 14. One (USS TANG, commanded by Admiral O Kane) is confirmed sunk by MK 18 torpedo, and multiple others are suspected.
Most bugs were resolved by late 1943 (this is simulated in TMO with MK 18 growing more reliable in Dec43/Jan 44) but circle run risk remained throughout the war.
Night surface attacks are great. US subs began using the tactic on regular basis in mid 1943.
lol Yes S boat is a tough ride, definitely not suited for surface attacks. I modified the S Boats in TMO, they were deep diving tanks in stock and original TMO. Now, they are not. Still tough but will not go very deep before reaches crush depth.