How to separate two diastereomeric amines?
When you mentioned column chromatography I had to assume you meant flash chromatography or biotage, which by implication is normal phase. When people mention HPLC they are normally defaulting to reverse phase. Now, if you can get reverse phase TLC plates (C18 are available) , you could make some advances.  The issue though is then getting the silica and you also mention large quantities.  

Large lab scale to me is say, 50g plus. For this, I would advocate crystallisation,  but to guarantee some differentiation,  I would make salts with organic acids. Nitrobenzenesulfonate salts are renowned for giving well defined crystals.  

If you needed something to better differentiate again the two amines, I would try a camphorsulfonate salt (pick an enantiomer).  These tend not to be too expensive.  The salts then have different solubilities and the right solvent becomes a screening exercise. Otherwise, tartaric acid is very cheap and easy to salt break after crystallisation.