It looks like I am allocating too much memory to Redis. Here is a medium busy time:

Redis 3.2.12    76.29M of 10.00G memory used
99309 keys stored in db0

Any ideas as to how much I should allocate? 1G ?

Based on your existing stats, 1G should be more than enough.

I am having an issue where the "cache" reading in Redis is zero...see below:

 

I wouldn't worry too much about that - it's not an "issue". Caches are often just duplicating what is in the data store and since Redis can be used for the datastore natively, most things stored in cache don't need to be doubled up.

I also have Redis Cache = 0.
I made ticket support to my host company. They did an analysis and here's what they answered:

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" We have reviewed your request and confirm that Redis is being used effectively. We cannot confirm the reason for the administrative part of the site to write "Cache: 0", but we assume that this module sends a request to one of the bases available in redis. The keys and their values are distributed in different bases, such as they are stored, as you can see in the screenshot - many sessions.

We checked the information directly in the redis port for your user, successfully accumulating objects, and we see that even the cache hit rate is high enough for MISSs:

keyspace_hits: 147352670
keyspace_misses: 3603491

In conclusion - we see that the system correctly uses Redis and from the point of view of the hosting environment there is no obstacle to its optimal use. "

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I think these analyzes confirm what @bfarber said, ie. no issue with redis cache = 0.