My fiancé has a 12 year old dockson, and he is horrible! I cannot stand this dog at all. He goes in the house- intentionally, like on the heaters or clothes, and he's constantly tearing stuff up blankets and pillows, and he's always getting into the trash and stringing it across the house.

And I don't know what to do, we can't keep living like this but my fiancé won't get rid of him... and we've ran out of ideas to get him to behave.

Can someone please give me some ideas or something this is getting ridiculous!!

The dog is a senior and must side with your fiancée. If he gets given up his chances at a new home are slim to none.
Has he been to a vet to rule out health issues? I am thinking with laying on clothes etc maybe it is more comfortable for his old bones.
Is he only doing this when he is left alone? If yes it sounds like separation anxiety
As for the garbage we have a lid on ours and keep it in the porch so my pets can not get to it. Then I don't get frustrated at them for doing what most pets do (cats and dogs). We make sure things he likes to get into when we are not home are out of his reach... he loves kleenex and toilet paper. Put all clothes in the closet and dressers.

Why are there clothes laying ? Sorry, clothes all have places to go in my home, baskets for dirty, and so on, so if clothes put away, that is not a issue.

Is he being taken out regularly? Is this a new issue, or has he always been like this.

The dog acts this way because he wasn't trained and because he is probably left alone too much, as well as being OLD. It's a little late for training, and if neither of you knows how (it takes a lot of loving patience, not yelling or hitting), then just put up with it. Or leave your fiancé. Obviously he loves his dog, so I wouldn't issue any ultimatums if I were you.

Two simple facts: take him out a regular times (dogs know exactly what time it is, and they like routine) about 4 hours apart.
Give him his own chew toys. When he tears something apart, say no once sharply and then give him his toy, and praise him and pat him.
Dogs aren't like kids except for the fact that yelling isn't how they learn, it's by example and with kindness and patience.

So what, exactly, have you done to curb this?

I am going to say at 12, he is who he is. Has he always acted like this? I'm sure this isn't the first time you've met this dog.

I'm going to congratulate your fiancé for not wanting to get rid of his dog. Its not right or fair that your fiancé has to get rid of his dog because you've entered the picture and up rooted everyone's schedule.

Some dogs just do not do good with change. They hate it and will act out in horrible pays to let everyone know that they are displeased.

Because this is a 12 year old dog, a Doxie and because you are at your wits end... instead of wasting your money with obedience trainers and vet consults.. find a behaviorist and go to them for help and assistance with these issues.

I'm sorry this dog is being naughty. You can still work with a 12 year old dog.. its just harder, which is why I recommend a behaviorist, not obedience training.