Lol, if you have solved hard solipsism by all means invite me to the Nobel celebration!
If I were a brighter chap, I'm sure I'd find myself in the position to send you an invitation straight away, my dear fellow!

However, I find the mysteries of solipsism not only intransigent but also firmly embedded within the minds of many folks, and these mysteries are such that I can only but continue to ponder them ...
... thus, I (excuse the pun) doubt that I'll find the cure for anyone's hard solipsism any time soon, although I do at times surmise that a hardy slap to the face of the solipsist could be somewhat effective in helping him reacquaint himself (or herself) with some measure of reality, such as it is. But even if the solipsist isn't jolted back to a sense of realism by a slap, it might still remind him that other minds do exist--and that those other minds do mind that he doesn't seem to mind enough about the existence of other minds. Of course, the awoken solipsist could ask the other minds, “why?,” at which point he may well receive another hardy slap—but to the other side of his face, of course!
Isn't being human “wonderful”? (“Why?” indeed!)
It seems to me that if what we are left with is a contingent and relational understanding (not knowledge) of God then we might be circling back to Hume and the idea of linking our confidence in the belief to the evidence.
To some extent, yes, we are left with, or perhaps trapped in, a contingent and relational position to our understanding of God. But, as to Hume, I think he would have stressed that our imagination plays an accessory role to our respective “bundles” of apparent perceptual connection, and we arrive at some level of confidence through our imagination so as to avoid Pyrrhonianism, even though some doubts (questions?) remain. I might be tempted to slap Hume in the face, but that wouldn't be very Christian of me, now would it?
If it is the case that God exists and burdens our E-theories beyond what they can sustain then our recourse might be to punt to externalism to some degree. That is, we can be as confident that our belief is true as the application of those beliefs seems to generate consistent and coherent results. So if my theory of God T suggests that action A produces result R then the consistency with which A produces R would be my measure of confidence in T.
Yes, I follow you. But at this point, pardon my apparent solipsism, I have to ask “why?,”--“why” I should drink your cup of T and not my cup of T? Moreover, what if we both soon find that we prefer to sip someone else's cup of T?

(Let's both ask the Mad Hatter, maybe he'll give us a sip of his cup of T for the sake of comparison?)
The objection that I would raise against myself immediately is that if it is the case that God is not the sort of thing that can captured by T then we don't have any way of attributing meaning to A or R.
Very sensibly put, Athee! In following your personal objections at this point, I'd say that we, by our own cognitive power, will only have contingent recourse by which to attribute meaning to A or R, and it is understandable that we all continue to wish to have a clear and distinct understanding of the T that we each think we have, respectively--a clarity probably never achieved by any fellow human being, at least, not by their own cognitive powers alone. (Excuse me a moment, Athee, while I ask our dear fellow Descartes to move to the next seat, which happens to be available on the other side of the table ...)
That is, if it is possible on T that in the event of a both R and not R can be shown to be internally consistent with T, then any sort of confidence level becomes an exercise in futility as there is simply no way to get anything other than a positive result.
To some extent, you're right. And, to some extent, I think Quine and Jesus would have an epistemic agreement with you … but there remain various epistemic contingencies for T that could mediate both R and not R and the outcomes of our apparent situation of “futility” ...
… that is, if various “contingencies” can be attributed to the set “any T” [T1, T2, T3, T4, T5 …] (let's call this CAT), contingencies typical of the human cognitive situation, both internally and externally that may mediate “any T”—then there may still remain at least one contingent possibility that some contingent meaning CM will manifest itself as a part of CAT and thereby be imputed to both A and R. But again, I must reiterate, within CAT we are speaking of contingent possibility; and this should be analytically differentiated from the confines of meaning we typically use when conceptualizing a state of affairs involving “possibility.”
Am I making sense, I'm not sure anymore...time to go read Kant some more, at the very least he will make me feel like I communicated my ideas clearly by comparison!
Yes, you make very good sense, Athee! And I understand your craving for assurance, cogency, and realism; it's a natural human proclivity, one we both share.
And yes, it may be time to read Kant; he makes for very interesting and useful study. I also think he was on to something substantial epistemologically, although I wrestle with his conclusions about Transcendental Idealism.
Now, the question remains, “Would you like another cup of T?” If so, you'll have to decide into whose cup you'd like the T to be poured and as to who will be doing the pouring.
Peace,
2PhiloVoid