
Hello Louise,
I wanted to add my very sincere condolences on your husband's death.
Dogs are often affected by loss in their human family and even the normally most well behaved and well adjusted can become stressed and act out of character. Your GSD is of course still very young and so this in part will be contributing to the behaviour but it's worth acknowledging that it can be multiple things building up which have caused the destructive behaviour.
I'd opt for having the Dachs in a larger play pen if possible rather than a cage so that they and also the GSD can enjoy stuffed kongs etc without fear of one eating everything or protective behaviours.
I'd also recommend that you give each of the dogs or areas in which they are kept something of your own clothing which is worn and so smells of you. That may give them some comfort to snuggle up with.
DAP collars and/or plug ins may be useful - the plug ins require to be on 24/7 within a reasonably confined area of the home where the dog(s) spend most time. Collars would cover periods when separated and of course walks. There are also DAP sprays which may be useful to apply to their bedding too.
Our pets also pick up a great deal from our own emotions and yours must be very fragile just now :( It will take a long time for you to build any form of normality into life but I'd say don't try and hold back your emotions for your own sake first and foremost and, further down the line of priority, the dogs too.
As to exercise, tired minds often help relieve boredom better than tired bodies. If you can give the dogs a mental workout a couple of times a day on top of what exercise you can currently provide this should help a lot. Increasing only physical exercise to countermand a behaviour can actually make things worse as we build up the dog's stamina so it requires ever increasing exercise to remain calm and content - sometimes beyond what even the most energetic and dedicated owner could ever provide :)
I hope that something from this or other contributors helps a little.
Prayers are being said for your strength of mind, body and spirit and that your husband's spirit is in a better place than us.
God bless, Teri x