I like the latest version of the postcard picture, including the lettering. The fact that the lettering is “imperfect” adds a vintage charm.
Having only limited and equally frustrating experience with rubber stamping, I hesitate to interject… but I must ask: what ink and inking pad are you using. I had to fiddle with different ink pads and inks to get good stamps. In the end, it also seemed like the rubber stamping had a break-in period before it would reliably work. I gave up and outsourced to a local crafter whe specialized in that aspect of crafting. Less frustrating for me and a much higher success rate.