Sorry for the long wait. Another sensei should have picked this up while I was gone due to irl circumstances. We'll continue from where we left off.
As for your first question, these cursed techniques require mediums for the curses to be cast. This medium is through the blood you either ingest or smear on the doll and the insignia you stand within. Without the blood of your opponent, the curses would have nothing to target. Secondly, there are ways to make it easier to deploy the insignia through customs, but that is for you to figure out how to do.
To answer your second question, you do not become linked to the doll. Only the doll and the opponent become linked, and half of any physical damage done to the doll will be done to the opponent.
Here is the last technique, which deals damage to the opponent from spiritual techniques such as genjutsu, Yamanaka, certain Yin techniques, and Ronin techniques that you also take due to becoming spiritually linked. List the advantages and disadvantages of this technique, and how you'd counter if it was used on you.
( Jujutsu: Seishin Hizumi Hyōketsu ) - Curse Technique: Mind Distorted Possessed Blood
Type: Offensive
Rank: Forbidden
Range: Short - Long
Chakra: 50 ( -20 per turn )
Damage: N/A ( dependent on jutsu used )
Description: In order to use this jutsu, the user must first create the Jashin insignia, a large 4 meter circle with a triangle on the inside, on the ground with his own blood. The user must remain in the center of the circle throughout the jutsu in order for the Curse to continue to work. After obtaining the opponent's blood in some way, the user ingests the blood and smears some on his face which becomes black with various white markings that commonly resembles skeleton, a symbol of death. Once the sacrificial ritual has been done, the victim and the user are spiritually linked. Any mental or spiritual harm that the user takes will be reciprocated on the opponent, ranging from Genjutsu to Yamanaka techniques.
Note: This jutsu lasts 3 turns and can only be used once every 4 turns.
Note: This jutsu can only be used by Jashinists.