Can I install Whole Home Surge Protector into two single pole breakers?
That's what happens when Mr. Snippy gets into a panel and makes all the wires "neat" for the inspector, as if there were brownie points for that.  Hots and Neutral should be able to reach any space in the panel, neutral because of GFCIs.  

Simply extend the wires with wire nut splices - it's ugly (by Mr. Snippy's standards), but it's no big deal electrically. 

Can you use two 1-pole breakers on a 120/240V load? No.  As someone who accidentally bought a bunch of 30A 1-poles that are practically useless, I've researched this at length. 

The two-pole breaker is because you have 2 hots and a neutral powering a single device.  Also, you want the amperage of the breaker to be fairly large so the surge suppressor can do its job - 15A is smaller than I'd want.  You're talking about a $10 breaker either way, so just use the one they recommend in the labeling and instructions - which is 30A.  And use an Eaton brand breaker (CH if your handles are Cutler Hammer beige, otherwise BR).  Do not use other random hardware store brands, no matter how much the clerk insists they'll fit.  That isn't brand loyalty, it's busbar compatibility).