Hello there, i am very interested on this project, i already worked with spot option api(banc de binary, interactive options, etc) and with tech financial api(tradorax - 24 option).
I also made already software to export signals from mt4 to a remote mysql database where the web app can read and trade to the binary brokers.
in addition to that, your site requires membership system, i see your budget pretty slow for me. i can develop the system in a 1 month period i think but i honestly don't think the job will end there, in a job like this there is at least 1 month more of work in testing and fixing problems.
the most brokers you add to the system, the most work and testing need to be done, even if they are under the sample api platform, they still have differences between them that need to be addresses.
i will suggest to start with the smallest amount of binary brokers possible.
anyways, i am really interested, we can maybe make it work somehow, please contact me to discuss more.