Email Deliverability, Server Settings and Spam Prevention

We have been having email deliverability issues and configuration issues. We're seeking someone to assist us in optimizing our server settings to achieve the best possible email deliverability. We'd like for you to understand our current email processes and advise of best practices and then also configure settings to achieve optimal results. We have an email mailing list of approximately 100,000 users that we segment and send email campaigns to on a weekly basis, as needed. Currently our monthly volume send needs to be approximately 400,000 emails per month and quickly we need to ramp this up to 1,000,000 sends per month or more. We have approximately 40,000 emails in Constant Contact with unlimited send ability. We can send approximately 30,000 emails per month through Zoho Campaigns and have just started building out a way to send through AWS using Sendy. I don't know which is the best ultimate way to go and we need a solution for this. I have heard about SendGrid and MailGun and also wonder if we should be using one of these services. I recently discovered when I performed a spam check in [login to view URL] that my spam score was 3.5/10 from Zoho and 7.5/10 from Constant Contact. This due to the following issues: SPF records did not match, DKIM not necessarily valid, we do not have a DMARC record, reverse DNS does not match with domain along with some other issues. We are not on any blacklists. I noticed on a campaign sent yesterday from Constant Contact to 8,500 emails only 1.2% bounced and only 8.4% opened, so I suspect a very high percentage ended up in spam. Also I was told by Constant Contact that Gmail is not receiving our emails and we do not know if this is a server configuration issue or a reputation issue. Also yesterday an Office 365 returned one of my emails as spam. I believe this had to do with having multiple SPF records. On a previous Zoho campaign of 30,297 emails sent we had 97% deliverability but only 12.9% open rate, so an 87% unopened rate. Only 0.4% unsubscribes and only 0.1% Complaints. Zoho Support gave me a series of DKIM to add to the DNS but I am hesitant because #1 I don't know how to add them and #2 I want to ensure our emails sent through zoho ONLY appear to come from our domain address and not a third party sender@ or mailer@ domain, which these appear to be related to. I need someone to resolve these issues in our domain and to rectify our email campaigns so that they aren't ending up in peoples spam box. We also would ultimately like to move our hosting from Go Daddy to a dedicated IP on Amazon. We need an expert who has experience in this to help with this migration and configuration. The right applicant will need to go into host make changes & troubleshoot until all spam errors are corrected. Only people with good english & who are experienced in spam set up handling need apply. This job is not just for someone to go into host & add some txt, it is for troubleshooting and expert level recommendations and support. This has the potential to develop into a long term support role to ensure our environment is functioning correctly and our email campaigns are structured property and deliverability is successful and conversion is taking place.