Welcome to the forum.
I'm sorry you feel discouraged.
What you are describing is entirely normal. Piggies are not cuddly animals, most don’t like being held and handled. They can enjoy a stroke in their cage, some will tolerate being held for a short while, but mostly they are happier just playing together rather than being held. I only handle my two boys for their weekly weight and health checks as they don’t like to be cuddled.
Unfortunately they aren’t really suitable to be childs pet. They can be expensive in vet care.
There are things you can try to communicate with them but they may still never like to be held. One of the first steps in gaining their trust is offering food from your hand. If you can offer food to then from your hand and they will take it, then they do trust you. This step can take a varying amount of time though - weeks, months etc. The most nervous of my two boys took 18 months before he took food from me and stopped running away terrified every time I went near them.
To pick them up, herding them into a carrier is best. Most piggies wont like being picked up as it comes too close to their prey instinct.
How To Pick Up And Weigh Your Guinea Pigs Safely
Understanding Prey Animal Instincts, Guinea Pig Whispering and Cuddling Tips
They do poop a lot and its actually very good as it means they are eating plenty of hay - a piggy who isn’t pooping is unwell. They cant be litter trained so seeing poops everywhere in the cage is what will happen. It is a lot of work in cleaning out and does take quite a bit of time.
Please don’t use preventative anti-parasite treatments on them. Products you can buy from a pet shop aren’t prescription strength so are not strong enough to deal with an active problem - they also won’t stop them from catching mites. Active mite cases need to have a treatment at the correct interval to stop the life cycle of the mite. The once a month preventatives won’t do that. Using them routinely can lead to resistance forming making it much harder to treat an active infestation.
If they are shedding excessively (remembering some shedding is normal), then they do need to see a vet.
Should they ever have an active case of mites, then they do need to see a vet to have prescription strength treatments as part of a course with the correct gap between each dose.
New Guinea Pig Problems: Sexing & Pregnancy; URI, Ringworm & Parasites; Vet Checks & Customer Rights
It’s perfectly fine to keep two boars together, but any bond comes down to character compatibility - they will fall out if they do not have compatibility. There are so many of us on here who do have boar pairs - sadly though they have an unfair reputation as being difficult
Showing normal dominance behaviours (chasing, mounting, rumbling) is entirely normal and not annoyance. You do not need to separate for these behaviours. My own boar pair are coming up 4 years old, they love nothing more than rumbling and chasing each other - it’s normal boar behaviour!
Ensuring boars have a lot of space is essential. They are more territorial and require a 180x60cm (6ft x 2ft) hutch on a single level to have enough room. Lack of space can mean they can’t get away from each other so can mean they get wound up more and at worst lack of space can contribute to break a bond.
However, it’s obvious when a bond has broken down - there will most likely be full on, rolling around, blood drawing fights. This sadly requires permanent separation.
A Comprehensive Guide to Guinea Pig Boars
Boars: Teenage, Bullying, Fighting, Fall-outs And What Next?
Dominance Behaviours In Guinea Pigs
If they are outside, then do ensure they are kept warm enough using lots of hay, thermal hutch covers and snugglesafe heatpads
If you really don’t feel they are the right pets for you, then surrendering them to a rescue centre for rehoming is best.
Getting Started - New Owners' Most Helpful Guides
Rescue Locator