As for the titles being lost on succession, that's because you have a Gavelkind law. While it allows you to have a larger demesne, it means you'll lose your titles when you die. I personally change to elective as soon as I can.
Stalin when trying to find a wife/husband for someone you want to marry them to someone with the same rank or higher like a prince to a princess or a baron to a baron etc.
In taberna quando sumus
non curamus quid sit humus,
sed ad ludum properamus,
cui semper insudamus.
Quid agatur in taberna
ubi nummus est pincerna,
hoc est opus ut queratur,
si quid loquar, audiatur.