Interesting game, nice art and a good take on the RPGM engine (feels well refined).
The cover-to-cover sniper segment is actually quite easy to compleate. The key is to either make a run in one go by constantly moving between covers, or if you stayed behind the cover for too long planning your next move or waiting for the zombie to pass over, simply step out and step back behind it which will draw out the next sniper shot. Personally I think that the second approach is quite fitting for the situation.
One mechanic / design choice that I am questioning is the use of TP pool to make a weapon reload. Using game currency in the mid of combat is a nice touch, but spending equally as much TP in the process is an overkill in my opinion (especially for Alice since the LMG reload takes her entire TP pool). Also, the reload skill-tip does not make any reference to TP costing, only the number of bullets to be used are mentioned. I recommend to either remove the use of TP for reload (makes use of combat skills more appealing in the process), or reduce the cost and perhaps make it more universal between different kinds of weapons (?).
Another aspect that I would recommend revisiting is your companions not recovering their HP, MP and TP between the missions. Based on the first mission with Scarlet, she retains the pools as they are at the start of the second mission. MC is not the leader/care taker of the group (yet?) and I do not question (though I should) the fact that team is using your bullets when reloading their guns, and using your crafted components free of any compensation (monetary or sexual *wink-wink*), but I am questioning them not taking care of themselves by filling-up their pools between the missions. I don’t believe that implementing recovery of pools on their end would make a major impact on the game difficulty, but it will make more sense story wise (they are also getting payed, right?).