Question on Hydrogen Balloon
Hydrogen, having very small and fast moving molecules,  diffuses faster and through smaller holes than air. Your balloons seem to be permeable for hydrogen. Try a different brand, if it helps. But as others have mentioned, rubber is not the best material to keep hydrogen. Better is a metallised plastic.
Pure hydrogen just burns in a flame.  If you have ever  watched the film footage (1937)  of the catastrophic accident of the airship Hindenburg , it was just a huge scale of burning in a flame.
What makes an explosive &quot;bang&quot;is a hydrogen mixture with air, even better with oxygen. Because  hydrogen does not explode, until is contains &gt;6% v/v of oxygen.
Any binary chemical explosion of gases requires a self-sustaining chain reaction. That does not happen if a mixture contains too little of one of mutually reacting gases.