After many tests, I developed a design that passes on test of time, and correct under heraldic rules. It's similar to design above, but with many slight corrections. Here's an emblazonment (depiction) made by myself:
l will explain it by parts (this quick glossary can be very useful):
Escutcheon (shield): Very similar to the draft, but with different chief (superior part). I blazon it this way (other variants are possible):
Per fess Or ermined Azure and Azure, on chief a lion passant guardant Pourpre armed and langued Azure, on base a cross moline Or.The draft contained a ultra-rare tincture (color) called Amaranth, between the pink and the purple. To avoid it being confused with Gules (red) or Pourpre (purple), I adopted the Pourpre tincture instead.
The escutcheon is round in the bottom, the most used in Iberic Peninsula and Latin America.
The lion is canting or punning ("Leo" is also an abbreviation of "Leonardo") and the lion represents many virtues in most of cultures. The cross moline represents my religion (Christianism) and is also one of the most striking heraldic charges, in my opinion. The ermine spots grants that my design is unique, as they rarely occurs.
Crest: The same lion of the shield, but in a different position, holding the cross moline of the same escutcheon. The owl was removed in name of a more homogene coat of arms. I blazon it as follow:
A demi-lion rampant guardant Pourpre langued and armed Azure, holding between the paws a cross moline Or.Mantling and wreath (torse): Azure (blue) and Or (yellow), the main dark and light colors of my coat of arms.
Helmet: A gentleman (or commoner) coat of arms, to don't claim honors that I don't possess.
Motto: "Homines Sumus, Non Dei" (translation: We Are Men, Not God). Represents the humility, one of the virtues I value the most, and the sense that we must be strong in all situations.
Standard: A simple banner of arms. The idea is use it in more ceremonial occasions. The ratio of 4:5 seems to a gentleman.
Flag: To be used in less formal occasions. The base of the escutcheon.
I know that a golden cross moline in a blue background was used in other occasions; for example, a Lord Molyneux used it on English Civil War, although the cross had a less modern design. Where ambiguity can occur, the banner of arms can be used.
Comments, suggestions, requests are all welcome with pleasure.
Very special thanks to Paul James and Samuel McKittrick from Flags Forum, of whom without the advices and guidance my coat of arms couldn't reach such quality.