Wehrmacht just meams “armed forces” whereas Heer = Army.
Check out some “Osprey” books on miltary uniforms. You can get em at model/ hobby stores and they are pretty good and detailed.
Firstly for uniform, is it formal, in which case you would wear a “stepping out” uniform (the best you have with all your medals etc) or are you simply wearing you day to day sevice uniform?
An Offizierfeldmutze (officers field cap) would be essential regardless (every man wears a hat!).
epier.com/store/outpostflags … p?id=31890
Until 1940 badges of rank on the collar and shoulder straps were worn on great coats and also on Tunics. Service belt was worn over the top of the greatcoat
Being a member of the party in 1930 was optional (but encouraged). You usually wouldnt progress high up in the ranks if you wernt a party member. However 1930 being before Hitler became chancelor this enforcement of party membership was not so strong. So if he is a Colonel in 1930 then its reasonable to assume he may have been a serving soldier during WWI, so a better chance he may not be a party member. If you DO want to be a party member you could wear an NSDAP (party members badge) stick pin in your lapel. A round badge with the Swastika on a gold background and NSDAP engraved around the edge.
diggerhistory.info/pages-bad … badges.htm
Or a swastika armband.
Field gray trousers (straight legs, two side pockets and a front watch pocket) adjusted at the waist by a buckled strap and designed to be worn with braces. However officers had the option to wear Jhodpurs (riding trousers) and often did so to unless in active combat. These are of matching field grey.
A white shirt and black tie would be a must. Perhaps black leather gloves?
Officer’s field blouse may be an option (basically a field grey tunic with 2 breast pockets and two waist pockets with rank and services insignia on the collar, national emblem, rank shoulder epaullette insignia and service braids, medals/ citations, optional service cuff. This would be worn closed collar over the shirt and tie and under the great coat (which at this stage could be worn open collar). I can give u list of pre WWII medals if you like, pre WWII iron cross or a pour le merite.
Basically if you plan to never take off the overcoat, you could wear a grey suit jacket underneath. Under that the white shirt & tie. Any grey trousers would do but if you can get a riding pair…cool. Black boots on your feet.
In my opinion you REALLY need the officers cap, they all wore 'em and they make you readily identifiable as a german officer, without it you could be any military dude in a greatcoat. You can check out military stores, but they tend to be a bit pricy. Fancy dress stores often hire them and hat places (over here) sell bus drivers hats (grey with a peak but no insignia) that look very very close. Coin/ military medal traders often sell cheap replica NSDAP members badges ( about $5).
Hope that helps, just ask if you need more info…WWII military history is one of my passions.