about the characteristics showing in the cart ...

We actually started to add an option for that.
If you use a really recent version, you can just go in phpmyadmin and in the hikashop_config table add an entry with the namekey being characteristics_values_separator and the value being the separator you would like.

You would have to edit the file show of the view product and change the code to use the main product name instead of the variant name.

So replace:
echo $this->element->product_name;
by:
if(!empty($this->element->main->product_name)){
echo $this->element->main->product_name;
}else{
$this->element->product_name;
}

and:
echo $variant->product_name;
by:
echo $this->element->main->product_name;