Using columns on Advanced Search Filter, or using Multi Selector

Hello,
I wrote same question on wordpress.org forum, and I was suggested to write the question on this forum. So my apologies for duplicated questions. Please ignore wordpress.org forum.

I created ‘services’ check box field, and I use this to filter the search results using Advanced Search. It’s working perfectly, however I have a visual problem.
‘Services’ are just too long, if I click ‘Customise my Search’, the filter window pull down. Because ‘Services’ are so long, it covers the most of page.

Then I thought if I use multi selector rather than check boxes on Advanced Search Filter, then the look and feel will be much neater and clear. However Paolo mentioned already it’s confusing for users and not possible.

Then I thought how about if I divide check boxes to columns? then the filter window can go much shorter? Do you think it’s possible?

I’ll send you the details separately,
many thanks for your help in advance.