If Ultraman Taro was considered to be a parody of Japanese fairy tales; this series in fact, pays homage to Japanese fairy tales; despite the fact that Leo is known for being the darkest entry in the Ultra Series, the Breather Episodes make up for lighthearted moments.
During Leo's mock boxing match with Renbolar in episode 23, the kids make use of makeshift boxing cards. After three rounds, they skipped to 5 after 3. This makes sense, as Tetraphobia is a common superstition prevalent in Southeast Asian countries. In hindsight, considering this series being notoriously Darker and Edgier, also borders on Fridge Horror. As a number of innocent people get killed by monster and alien attacks on a regular basis. It's made even worse by Commander Black's introduction and the deaths of every MAC member, except Gen and Dan, setting in motion for the 11-episode endgame arc. Matters don't even help that the final appearance of all MAC members was in episode40.
If that leg injury had been worse, Dan could have been killed when he tried to transform again in Episode 1.
That Hand Blast that Alien Magma shot Seven with may have been the cause of the Ultra Eye's destruction and not so much the leg injury. The leg may have weakened Seven's immune system, so to speak, allowing Magma to do the real damage. What does the transformation sequence entail? Concentration of energy and force of will. Dan was weakened by the blast, plus his leg was broken, plus he didn't allow time to heal. His spirit is broken. His failed attempt to transform was painful. He was depressed, tearful, possibly angry. This is not Dan as we know him. It's not just the stress or the incident. Magma did more than defeat him or injure him.
Whoever decided to stand up the main MAC base in a space station (as opposed to establishing a detachment or small outpost there) DID know that at least one space station had been destroyed by aliens for each of the previous three teams (MAT, TAC, and ZAT). MAT lost two: one to Bemstar, and another to the Nackle aliens. TDF (the higher-ups for these teams) knew the danger inherent in space stations as military bases and yet did nothing to protect their soldiers or come up with alternative plans (i.e subterranean bases like the Ultra Garrison had back in the day). Dan Moroboshi certainly knew the risks; he must have witnessed or have heard first-hand accounts of these alien attacks.