switching current KVM server & tools to latest release on Leap 15.3

I have added the following repo into 15.3 in the hope to get the same or higher release version of KVM server & tools as found on the latest tumbleweed snapshot

 https://download.opensuse.org/repositories/Virtualization/openSUSE_Leap_15.3/ 

after the installation of this repo I was able to update some of the KVM packakes but not all of them by using

zypper dup --from KVM --allow-vendor-change

how can I fix this?

Below are all my repos

zypper repos --details 
#  | Alias                       | Name                                                                                        | Enabled | GPG Check | Refresh | Priority | Type   | URI                                                                           | Service
---+-----------------------------+---------------------------------------------------------------------------------------------+---------+-----------+---------+----------+--------+-------------------------------------------------------------------------------+--------
 1 | KVM                         | KVM                                                                                         | Yes     | (r ) Yes  | No      |   99     | rpm-md | https://download.opensuse.org/repositories/Virtualization/openSUSE_Leap_15.3/ | 
 2 | mozilla                     | mozilla                                                                                     | Yes     | (r ) Yes  | No      |   99     | rpm-md | https://download.opensuse.org/repositories/mozilla/openSUSE_Leap_15.3/        | 
 3 | repo-backports-debug-update | Update repository with updates for openSUSE Leap debuginfo packages from openSUSE Backports | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/update/leap/15.3/backports_debug/                | 
 4 | repo-backports-update       | Update repository of openSUSE Backports                                                     | Yes     | (r ) Yes  | Yes     |   99     | rpm-md | http://download.opensuse.org/update/leap/15.3/backports/                      | 
 5 | repo-debug                  | Debug Repository                                                                            | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/debug/distribution/leap/15.3/repo/oss/           | 
 6 | repo-debug-non-oss          | Debug Repository (Non-OSS)                                                                  | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/debug/distribution/leap/15.3/repo/non-oss/       | 
 7 | repo-debug-update           | Update Repository (Debug)                                                                   | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/debug/update/leap/15.3/oss/                      | 
 8 | repo-debug-update-non-oss   | Update Repository (Debug, Non-OSS)                                                          | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/debug/update/leap/15.3/non-oss/                  | 
 9 | repo-non-oss                | Non-OSS Repository                                                                          | Yes     | (r ) Yes  | Yes     |   99     | rpm-md | http://download.opensuse.org/distribution/leap/15.3/repo/non-oss/             | 
10 | repo-oss                    | Main Repository                                                                             | Yes     | (r ) Yes  | Yes     |   99     | rpm-md | http://download.opensuse.org/distribution/leap/15.3/repo/oss/                 | 
11 | repo-sle-debug-update       | Update repository with debuginfo for updates from SUSE Linux Enterprise 15                  | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/debug/update/leap/15.3/sle/                      | 
12 | repo-sle-update             | Update repository with updates from SUSE Linux Enterprise 15                                | Yes     | (r ) Yes  | Yes     |   99     | rpm-md | http://download.opensuse.org/update/leap/15.3/sle/                            | 
13 | repo-source                 | Source Repository                                                                           | No      | ----      | ----    |   99     | NONE   | http://download.opensuse.org/source/distribution/leap/15.3/repo/oss/          | 
14 | repo-update                 | Main Update Repository                                                                      | Yes     | (r ) Yes  | Yes     |   99     | rpm-md | http://download.opensuse.org/update/leap/15.3/oss/                            | 
15 | repo-update-non-oss         | Update Repository (Non-Oss)                                                                 | Yes     | (r ) Yes  | Yes     |   99     | rpm-md | http://download.opensuse.org/update/leap/15.3/non-oss/ 

instead of the virtualization repo I added I guess I should had added the pattern kvm server/tools repos instead, unfortunately there is no experimental package for Leap 15.3 so I was wondering if I could use the tumbleweed official release repos on leap 15.3?

Why no refresh for the Repos?
If you enable a Repo use refresh to get it up to date.

Otherwise disable and delete the Repo.

I did do a refresh prior to dup, but Im still wondering which is the correct repo for kvm or can I use the repo on tumbleweed on leap?

If you add Tumbleweed (TW) repos to Leap, then, after some updates, OS will change some repos from Leap’s to TW’s. And you’ll get broken OS with some packages from Leap, and some packages from TW.
To use TW packages with Leap download needed packages into some folder, add this folder as a repository, then install needed software from this repository.
Installer will complain about absence of signature for packages - ignore this (or create signature for your “repo”).
TW uses glibc and other stuff newer than Leap’s - this may cause some problems.

Another possibility: compile needed software by yourself.