Some words I'm not understanding


So this is from the manga Kochikame:

![Kochikame](https://i.stack.imgur.com/lpX9G.png)

Basically the guy on the ground was asking the cop directions while the cop
was listening to a horse race on the radio and found out his horse lost.

Anyway, in this sentence what does "スって" mean? The closest I can find is "吸う,"
like he was absorbed in the race, but is that right?

Next, "頭にきてる" is another phrase I'm unfamiliar with. [This
link](http://ejje.weblio.jp/content/%E9%A0%AD%E3%81%AB%E3%81%8D%E3%81%A6%E3%81%84%E3%82%8B)
says it means mad, so is this a set phrase or what word is きてる coming from?

Then finally, what does "だてに" mean? The closest I can find is "伊達" which seems
weird in this sense. And "ぶらさげてる," in this context it means like his gun isn't
hanging from his holster, right?

Lotta questions there, so I appreciate any help I can get, thanks!

* * *

_For accessibility purposes, I've included a transcription. The angry
policeman says the following:_

> 競馬で スって  
>  頭にきてる時に  
>  ゴタゴタぬかす  
>  と 本当に  
>  ぶっ殺すぞ！
>
> だてに拳銃を  
>  ぶらさげてるんじゃ  
>  ねえんだぞ！

_And then the man on the ground says:_

> わっ
>
> わかっ  
>  たす！




I'm not super confident in this answer, so if it's wrong I'll delete it.

The first part I believe is something like "When you come talk all this
nonsense to me when/after I had lost money on the horse race and am losing it,
I could just kill you!"

The `スって` I believe is from `[擦]{す}る`, and my dictionary has the example
`[競馬]{けい・ば}で大金をする` as "lose a lot of money in the horse race". `頭に来る` is a set
phrase meaning "go crazy"/"get worked up" as you mentioned. And `ぬかす` is a
slang form of `言う`.

