Improvised weapons are mostly left to the DM. There is very little that we can tell you for sure; you will have to ask most of these questions to your deputy minister.
Improvised weapon in melee and remotely
A weapon can count as both a melee weapon and a ranged weapon; many weapons to launch do it. An improvised weapon might be the same: you can hit a brick against someone's head, or throw a brick on someone, and both attacks would be attacks with an improvised weapon. On the other hand, while, in the appropriate fantasy setting, we can imagine a playing card jetty that could hurt someone, I can not imagine how you can hit someone with a card in melee that could hurt him. (The mere fact of hitting them with the card wrapped around the fist probably does not count.) Your DM may or may not allow it, but that will probably depend on whether or not they can imagine it hurting someone.
Mastering melee weapons and controlling ranged weapons with dropped weapons
Anyway, if they are allowed, the thrown weapons can be both a melee weapon and a ranged weapon, and the wording of Melee and Ranged Weapon Mastery is that you get the bonus when using the appropriate weapon type, regardless of the type of weapon used. of attack that you do. And, officially, they pile up. So, you could get +4 to attack and damage with a discarded weapon if you took both. However, you should ask your DM because some DM may find it derisory to have both of them like that. Personally, given that you have accomplished four feats on this subject, I do not think it is a very strong choice, even if your DM allows it – the focus on weapons, the specialization of weapons, the control of melee weapons and the mastery of ranged weapons are rather weak prowess.
Magic improvised weapons
To become magical, a weapon must first be a master weapon. An improvised weapon is, by definition, something that was not designed to be a weapon. If you made a card designed to be a weapon and designed with the quality of a masterpiece, it would no longer be improvised – it would be a real weapon. Whether it is possible or not in your gaming world depends on your DM.
Ask your DM for sophisticated, perhaps exotic, weapons that are actually playing cards. Sharpened metal edges, perhaps. Use the statistics for a dagger, maybe. Then you can get masterpiece versions and add magic without asking any questions. Having Actually Improvised weapons are a bad idea – there is really no benefit in using them, I checked.
In addition, you probably should not take Weapon Focus unless something really good does not require it. You probably should not take four levels of fighter – a feat per level for the first two levels is acceptable, a feat for all other levels is really low. And even if you do, you certainly should not be following the specialization of weapons. This destroys the feats of gun control, but they are not so good anyway. Instead, I recommend looking in Launcher Master's Complete Warrior. Blade of the bloodstorm of Battle Tome is pretty good to launch, too. If you want to be based on strength, the brutal throwing of Complete adventurer is good and the rangers can make you perform dual-use exploits or remotely without Dexterity. If you want to be based on Dexterity, Dead Eye's Compendium of the Dragon can deal damage to Dex, and if you treat the cards as if they were daggers, Shadow Blade's Battle Tome will also be (they stack). The sword is useful for getting Shadow Blade and can also allow you to do more useful things.