How long has this been going on?
If you know that he's vomiting on an empty stomach, you can somewhat help this by never letting his stomach empty. Offer him food at night before you walk him one last time and then feed him when he wakes up. You might even want to give him a bland diet when he has flare ups. Boiled chicken and white rice is a great choice (no bones, no skin). Some vets will recommend that you go so far as offering tagamet or pepcid to help with reflux if this is an underlying cause.
This would be a good time for a fecal exam to rule out parasites as the cause of the nausea.
For immediate relief, keep him from eating any grass any let his stomach rest. (They seem to like it when their stomach is upset) Then offer some pedialyte and see if he can keep it down.
If he can't or this does not resolve quickly, give your vet a call.
Let me know if you still have questions.
Blood in the fecal matter can have a lot of causes. The most common and most likely is a parasite problem. I suggest that you go ahead and see the vet as soon as you can for a fecal exam to rule this out, even though you have done it once. Whip worms are often missed on a fecal exam.
Aside from that, intestinal obstructions and other problems can cause blood in the stool as well.
You can try switching him over to a bland diet of only boiled chicken and white rice until it improves. Then you can start to add his regular food back in.
If he's lethargic, can't keep anything down (even the bland diet) or seems to have neurological symptoms, you need to see your vet soon.
If you switch his food around a lot (treats, table scraps, etc) this might be your cause.
Try the bland diet today and see if it resolves any. If not, or the symptoms worsen, you will need to make an emergency visit to your vet this afternoon.
Does the lump wiggle under your finger like a marble?
This could have a lot of causes, unfortunately. The most common is a fatty tumor or lipoma. They are very common in some breeds. If this is the case, the lump might move freely under the skin or wiggle under your fingers like a marble.
Aside from that, other tumors, bug bites and even traumas to the skin can cause a lump.
Tumors are not typically painful, if that makes you feel any better.
I would go ahead and see the vet tomorrow for a fine needle aspiration to find out what you're dealing with and then go from there. They can usually do this right in the office.
But my bet is that this is a lipoma.
Let me know if you still have specific questions!
You're very welcome!