You can always make it appears only for the first day to night and then night to day transitions, pausing the game only once for each of these 2 messages would make it a homage to the original while also not enraging anyone afterwards with subsequent pauses.
1. Would you like enemies to spill blood if hit? ( if the enemy is the type that does drop blood )
Yes, obviously only if they have flesh.
2. Metroidvanias often limit heart max, would you like to see heart max locked to level in Simon's curse? ( so you don't farm 500 hearts for every boss. Remember gold and hearts are different, buy with gold. )
Yes like in the old games its better to have a limit, more than 99 hearts on the start of the game isnt a good idea since you could spam sub-weapons.
3. Would you like to see armor items in game? ( old one had resistance that increased by level )
Yes, but balance enemies and bosses with these armors in mind, otherwise it would be too easy or too hard.
4. Would you like Simon's curse to have very hard to know secrets/easter egg items or/and places? ( Well you know how these things work )
Secrets are very important, if you could add a area with a secret enemy or boss it would be even better, otherwise just a NPC?
5. Game better very hard or just normal difficulty? (I'm not adding difficulty slider, harder new game+ MAYBE)
Normal difficulty, but no so easy like in SotN. Try to do something like Order of Ecclesia nearing Circle of the Moon.
6. Thing you would like to see in this game? ( items, enemies, bosses, places, characters, etc)
Simon's house and Belmont's Graveyard.
7. Would you like there to be rare hp potions that cant be bought only found in secret places max 3 carry? ( how much they would heal? I dunno that has to be balanced, currently thinking 30%-50% hp )
Yes, would be a good homage to MSX Vampire Killer's hidden shops but as some users stated, beware to not make bosses too easy because of this. These should be like a reward to less skilled players to be able to finish the game, while doesnt making it a "cake walk".